feat: model picker.

[knightedcodemonkey]

• refactor: github controls, drawers, controls.

[Copilot]

Pull request overview

Adds a GitHub Models “model picker” to the AI chat drawer and refactors related GitHub controls/drawer layout to better fit responsive breakpoints.

Changes:

• Introduces a chat model selector UI and threads the selected model through streaming + fallback GitHub chat requests.
• Adds a local list of model options (to avoid CORS issues when querying model catalogs directly).
• Updates responsive drawer/control styling and adjusts existing Playwright assertions for updated labels.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/styles/layout-shell.css	Tweaks AI toggle visibility behavior and hidden-state handling across breakpoints.
src/styles/diagnostics.css	Updates mobile drawer sizing/positioning constraints.
src/styles/ai-controls.css	Refines AI chat drawer layout and adds styling for the new model picker control.
src/modules/github-chat-drawer.js	Adds model selection plumbing, model-aware error messaging, and propagates model into API calls.
src/modules/github-api.js	Defines default model + model options list; returns model used by API responses; defaults model param consistently.
src/index.html	Updates labels/copy and adds the model <select> to the AI chat drawer markup.
src/app.js	Wires the model select element into createGitHubChatDrawer and forwards token updates.
playwright/app.spec.ts	Updates tests to match renamed “ShadowRoot” label.

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