fix: pin subagent model and unify desktop UI (#211)

## Related Issue

Resolve #209
Resolve #210

## Problem

The subagent-model setting looked authoritative, but it configured only
a default. An explicit primary-model request could still override it.

The shared sidebar selected different banner assets by theme instead of
using the approved dark banner across browser and desktop builds.

The desktop updater did not match the approved prompt and progress
design. Electron's differential download could also fail and fall back
to a second full transfer, which restarted the visible progress.

## What changed

- Add an accessible switch that writes the canonical v2 `defaultModel`
and `force` fields while reading legacy `model` values.
- Use `pythinker_banner_dark.svg` in the shared web, macOS, and Windows
sidebar, and remove the unused light code-banner asset.
- Match the reference updater prompt and progress layout with Pythinker
branding.
- Force one full update transfer and ignore late progress events after
the update is ready.
- Keep an available update downloadable when automatic checks are
enabled.
- Add regression coverage and rebuild the committed web bundle.

## Verification

- `pnpm test apps/pythinker-web/test` — 84 files, 999 tests passed.
- `pnpm test apps/desktop/tests` — 14 files, 170 tests passed.
- Web and desktop typechecks, `tsgo`, and `pnpm lint` — passed with 0
errors.
- `pnpm run build:web` and `pnpm run check:web` — 673 bundle entries
verified at source hash `f88e4160eddd`.
- Built-browser security checks — Mermaid and Monaco sanitization
passed.
- The signed macOS package passed strict `codesign` verification and
contains a byte-identical copy of the rebuilt web bundle.
- Available and downloading states were visually inspected against the
supplied desktop references.

## Checklist

- [x] I have read the
[CONTRIBUTING](https://github.com/PyModel/pythinker-code/blob/main/CONTRIBUTING.md)
document.
- [x] I have linked related issues.
- [x] I have added tests that prove the changes work.
- [x] Ran `gen-changesets` skill.
- [x] This PR needs no documentation update.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
  - Added options to select and force a default model for subagents.
  - Added support for additional diagram types and editor languages.
- Added automatic update-check controls and clearer update download
progress.

- **Improvements**
- Updated the update dialog with release dates, branded styling, and
responsive layout.
  - Standardized the sidebar with a consistent dark banner.
  - Improved update state handling and download reliability.

- **Bug Fixes**
- Prevented update progress events from showing incorrect download
states.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: elkaix

.changeset/pin-subagent-model.md

@@ -0,0 +1,5 @@
+---
+"@pymodel/pythinker-code": patch
+---
+
+Add a setting to pin every subagent to the selected model, use the dark banner in every sidebar, and show Pythinker desktop updates as one continuous download.

apps/desktop/src/updater.ts

@@ -264,6 +264,7 @@ function hasUpdateConfig(): boolean {
 function configureExplicitConsent(): void {
   autoUpdater.autoDownload = false
   autoUpdater.autoInstallOnAppQuit = false
+  autoUpdater.disableDifferentialDownload = true
   autoUpdater.channel = settings.channel === 'stable' ? STABLE_UPDATER_CHANNEL : settings.channel
   autoUpdater.allowPrerelease = settings.channel !== 'stable'
   autoUpdater.allowDowngrade = false
@@ -346,6 +347,7 @@ function wireUpdaterEvents(): void {
       })
     })
     autoUpdater.on('download-progress', (progress: ProgressInfo) => {
+      if (state.status !== 'downloading') return
       updateState({
         status: 'downloading',
         percent: progress.percent,
@@ -444,7 +446,7 @@ export function setAutoUpdate(enabled: boolean): UpdateState {
   }
   if (enabled) {
     scheduleChecks()
-    if (!wasEnabled) void checkForUpdatesNow()
+    if (!wasEnabled && state.availableVersion === undefined) void checkForUpdatesNow()
   } else {
     clearTimers()
   }

apps/desktop/tests/updater.spec.ts

@@ -30,6 +30,7 @@ vi.mock('electron-updater', () => ({
       checkForUpdates: vi.fn(),
       downloadUpdate: vi.fn(() => Promise.resolve([])),
       quitAndInstall: vi.fn(),
+      disableDifferentialDownload: false,
     },
   },
 }))
@@ -69,6 +70,7 @@ afterEach(() => {
   autoUpdater.autoInstallOnAppQuit = undefined as unknown as boolean
   autoUpdater.allowPrerelease = undefined as unknown as boolean
   autoUpdater.allowDowngrade = undefined as unknown as boolean
+  autoUpdater.disableDifferentialDownload = false
   ;(autoUpdater as unknown as { _channel: string | null })._channel = null
 })
 
@@ -241,6 +243,7 @@ describe('strict update consent', () => {
     expect(localAutoUpdater.allowDowngrade).toBe(false)
     expect(localAutoUpdater.autoDownload).toBe(false)
     expect(localAutoUpdater.autoInstallOnAppQuit).toBe(false)
+    expect(localAutoUpdater.disableDifferentialDownload).toBe(true)
     expect(localAutoUpdater.checkForUpdates).not.toHaveBeenCalled()
     expect(localAutoUpdater.downloadUpdate).not.toHaveBeenCalled()
     expect(localAutoUpdater.quitAndInstall).not.toHaveBeenCalled()
@@ -339,6 +342,7 @@ describe('strict update consent', () => {
     const {
       getUpdateState: getLocalUpdateState,
       initUpdater: initLocalUpdater,
+      startUpdateDownload: startLocalUpdateDownload,
     } = await import('../src/updater')
     vi.mocked(localApp.getPath).mockReturnValue(directory)
     Object.defineProperty(localApp, 'isPackaged', { configurable: true, value: true })
@@ -366,6 +370,7 @@ describe('strict update consent', () => {
       releaseDate: '2026-08-22T12:00:00.000Z',
       releaseNotes: [{ note: 'First change' }, { note: null }, { note: 'Second change' }],
     })
+    startLocalUpdateDownload()
     progress?.({ percent: 42.5, transferred: 425, total: 1_000, bytesPerSecond: 85 })
 
     expect(getLocalUpdateState()).toMatchObject({
@@ -381,6 +386,38 @@ describe('strict update consent', () => {
     })
   })
 
+  it('keeps an available update downloadable when automatic checks are enabled', async () => {
+    vi.resetModules()
+    const directory = temporaryDirectory()
+    writeFileSync(join(directory, 'app-update.yml'), '', 'utf8')
+    writeFileSync(join(directory, 'update-settings.json'), '{"autoUpdate":false}\n', 'utf8')
+    const { app: localApp } = await import('electron')
+    const { default: localElectronUpdater } = await import('electron-updater')
+    const {
+      getUpdateState: getLocalUpdateState,
+      initUpdater: initLocalUpdater,
+      setAutoUpdate: setLocalAutoUpdate,
+      startUpdateDownload: startLocalUpdateDownload,
+    } = await import('../src/updater')
+    const localAutoUpdater = localElectronUpdater.autoUpdater
+    vi.mocked(localApp.getPath).mockReturnValue(directory)
+    Object.defineProperty(localApp, 'isPackaged', { configurable: true, value: true })
+    Object.defineProperty(process, 'resourcesPath', { configurable: true, value: directory })
+
+    initLocalUpdater(() => undefined)
+    const available = vi.mocked(localAutoUpdater.on).mock.calls.find(
+      ([event]) => event === 'update-available',
+    )?.[1] as ((info: { version: string }) => void) | undefined
+    available?.({ version: '1.2.3' })
+
+    expect(setLocalAutoUpdate(true)).toMatchObject({ status: 'available', availableVersion: '1.2.3' })
+    expect(localAutoUpdater.checkForUpdates).not.toHaveBeenCalled()
+    expect(startLocalUpdateDownload()).toMatchObject({ status: 'downloading' })
+    expect(localAutoUpdater.downloadUpdate).toHaveBeenCalledOnce()
+    setLocalAutoUpdate(false)
+    expect(getLocalUpdateState()).toMatchObject({ status: 'downloading' })
+  })
+
   it('downloads and installs only through separate explicit actions', async () => {
     vi.resetModules()
     const directory = temporaryDirectory()
@@ -420,6 +457,55 @@ describe('strict update consent', () => {
     expect(readUpdateSettings(directory)).toMatchObject({ pendingInstallVersion: '1.2.3' })
   })
 
+  it('does not return to downloading after the update is ready', async () => {
+    vi.resetModules()
+    const directory = temporaryDirectory()
+    writeFileSync(join(directory, 'app-update.yml'), '', 'utf8')
+    writeFileSync(join(directory, 'update-settings.json'), '{"autoUpdate":false}\n', 'utf8')
+    const { app: localApp } = await import('electron')
+    const { default: localElectronUpdater } = await import('electron-updater')
+    const {
+      getUpdateState: getLocalUpdateState,
+      initUpdater: initLocalUpdater,
+      startUpdateDownload: startLocalUpdateDownload,
+    } = await import('../src/updater')
+    const localAutoUpdater = localElectronUpdater.autoUpdater
+    vi.mocked(localApp.getPath).mockReturnValue(directory)
+    Object.defineProperty(localApp, 'isPackaged', { configurable: true, value: true })
+    Object.defineProperty(process, 'resourcesPath', { configurable: true, value: directory })
+
+    initLocalUpdater(() => undefined)
+    const available = vi.mocked(localAutoUpdater.on).mock.calls.find(
+      ([event]) => event === 'update-available',
+    )?.[1] as ((info: { version: string }) => void) | undefined
+    const progress = vi.mocked(localAutoUpdater.on).mock.calls.find(
+      ([event]) => event === 'download-progress',
+    )?.[1] as ((info: {
+      percent: number
+      transferred: number
+      total: number
+      bytesPerSecond: number
+    }) => void) | undefined
+    const downloaded = vi.mocked(localAutoUpdater.on).mock.calls.find(
+      ([event]) => event === 'update-downloaded',
+    )?.[1] as ((info: { version: string }) => void) | undefined
+
+    available?.({ version: '1.2.3' })
+    startLocalUpdateDownload()
+    progress?.({ percent: 100, transferred: 1_000, total: 1_000, bytesPerSecond: 80 })
+    downloaded?.({ version: '1.2.3' })
+    progress?.({ percent: 1, transferred: 10, total: 1_000, bytesPerSecond: 20 })
+
+    expect(getLocalUpdateState()).toMatchObject({
+      status: 'downloaded',
+      availableVersion: '1.2.3',
+      percent: 100,
+      transferred: 1_000,
+      total: 1_000,
+    })
+    expect(localAutoUpdater.downloadUpdate).toHaveBeenCalledOnce()
+  })
+
   it('does not let a scheduled check overwrite a downloaded update', async () => {
     vi.useFakeTimers()
     try {

apps/pythinker-code/dist-web/.web-bundle-manifest.json

@@ -1,4 +1,4 @@
 {
-  "sourceHash": "965c37d0a139928c9e6107941d28eb228a6be4d212d1bbd110338a83ef8646a2",
-  "sourceFileCount": 404
+  "sourceHash": "f88e4160eddd99fef98d31820eb0a5e660fc8209a97edb99e62b445d7f9b7365",
+  "sourceFileCount": 403
 }