chore: add changesets for the extension design overhaul

Author: elkaix

.changeset/vscode-chat-fixes.md

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+---
+"pythinker-code": patch
+---
+
+Render long conversations with a virtualized list, fix control overlap at narrow sidebar widths, and make sign-out work from the command palette.

.changeset/vscode-composer-menu.md

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+---
+"pythinker-code": minor
+---
+
+Combine permission mode, plan mode, and thinking effort into one composer menu, and answer approval prompts with number keys.

.changeset/vscode-config-hub.md

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+---
+"pythinker-code": minor
+---
+
+Add a config hub page that shows models, providers, MCP servers, the local config file, and extension settings in one place.

.changeset/vscode-editor-theme.md

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+---
+"pythinker-code": minor
+---
+
+The extension UI now follows the editor color theme, including light, dark, and high-contrast themes.

.changeset/vscode-host-integrations.md

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+---
+"pythinker-code": minor
+---
+
+Add a status bar indicator, quick-fix code actions, terminal and editor context menu entries, a getting-started walkthrough, and a new-conversation keybinding.