fix: restore reliable click-to-position cursor in 1.4.3

[HelloThisWorld]

Summary

Prepare the stable winTerm 1.4.3 hotfix and restore reliable Click to position cursor behavior when normal pointer jitter occurs between button press and release.

This PR was created as a draft because automated interaction coverage and OS-injected real-window validation passed, but the required physical-mouse validation and the five clean prompt-lifecycle repetitions are still explicitly NOT RUN. GitHub records that the repository owner merged it at 2026-08-27 00:11:07 UTC before that manual gate completed. No build label was added; tag creation and release publication remain blocked on the gate.

Related issues

No linked issue.

Detailed changes

Root cause

PointerPressed
  -> sub-threshold PointerMoved
  -> SetEndSelectionPoint called without an active selection
  -> selection-copy state marked dirty anyway
  -> PointerReleased rejected cursor repositioning
  -> stale state could poison later clicks

The Core correctly ignored selection-end updates when no selection existed, but Interactivity still treated each pointer move as a real selection change. That unrelated copy state then blocked release-time cursor repositioning.

Fix

• Extend the selection endpoint only after crossing the existing drag threshold or while a drag selection already exists.
• Make ControlCore::SetEndSelectionPoint report whether it actually updated a selection.
• Mark CopyOnSelect state dirty only after a real selection update.
• Decide plain-click repositioning from its own pending gesture state and normalize stale copy state when no selection exists.
• Preserve existing Ctrl+Click, VT mouse, Shift+Click, double-click, triple-click, drag-selection, coordinate, padding, buffer-bound, editable-mark, full-width-glyph, and split-pane precedence and safety checks.
• Add regression coverage for sub-threshold movement, repeated clicks, poisoned-state recovery, threshold boundaries, CopyOnSelect ownership, and stale copy state.
• Advance all authoritative application, package, shell-module, Windows-resource, workspace-fallback, documentation, release-note, and validation references to stable 1.4.3 / 1.4.3.0 / v1.4.3.
• Document that release installers are not Authenticode-signed and may trigger Unknown Publisher or SmartScreen warnings.

Validation performed

Environment: Windows 11 x64, local Microsoft Terminal-compatible toolchain, Debug and Release x64.

• Focused *CursorReposition* tests: 11/11 passed.
• Debug relevant suites: SettingsModel 245/245, TerminalApp 51/51, TerminalControl 100/100.
• Release relevant suites: SettingsModel 245/245, TerminalApp 51/51, TerminalControl 100/100.
• Full Release x64 application and test build: passed.
• Smoke validation: passed.
• scripts/winterm/verify-version.ps1: passed.
• scripts/winterm/verify-branding.ps1: passed.
• scripts/winterm/test-visual-progress.ps1 -SourceOnly: passed.
• Unpackaged Release staging/layout and branding validation: passed.
• OS-injected real-window supplemental validation: 30/30 command insertion/readback clicks passed, including actual 1px movement, beginning/middle/end positions, 20 paced clicks, and 10 rapid far-apart clicks. Paced drag, double-click word selection, and triple-click line selection also passed.
• Physical-mouse validation: NOT RUN.
• Five clean prompt lifecycles: NOT RUN because the validation window was closed before this gate was completed.

Checklist

• The change is focused and does not include unrelated formatting.
• Tests were added or updated where appropriate.
• All tests claimed above actually ran and passed.
• User-facing behavior and limitations are documented in this repository.
• This source/docs commit updates the root CHANGELOG.md.
• The Wiki Development-Changes.md ledger has been pushed with the final source SHA, link, summary, and checkpoint/release. (Wiki commit 7a39d28b40015ed149093a6264dabe0892a2a323.)
• Documentation screenshots reuse a suitable existing sanitized winterm-site asset, or no screenshot was added. (No screenshot added.)
• Version or schema changes include compatibility and migration notes.
• Package identity, winterm.exe, and Microsoft Terminal coexistence remain isolated.
• No command text, terminal output, clipboard content, credentials, or private paths are logged.
• New source and script files contain the appropriate MIT license header. (No new source or script files.)
• I did not include generated build output, secrets, certificates, or local absolute paths.