fix goose2 window minimum sizing

[wesbillman]

Category: fix
User Impact: Users can no longer resize the Goose2 desktop app into a state where the settings UI overlaps native window controls or clips essential content.
Problem: Goose2 allowed the desktop window to shrink below the space the app chrome and settings modal need, which made the settings screen overlap macOS traffic lights and crop content. The settings dialog also had a fixed 600px height, so small viewports could still produce broken layouts.
Solution: The Tauri window now enforces an 800x600 minimum, matching the app's launch size. The settings modal now fits within the viewport with margin and gives the settings navigation its own scroll area when space is constrained.

File changes

ui/goose2/src-tauri/tauri.conf.json
Adds minimum window dimensions so the desktop app cannot be resized below the size the shell is designed around.

ui/goose2/src/features/settings/ui/SettingsModal.tsx
Makes the settings modal responsive to viewport height and width, and makes the settings navigation scroll independently to avoid overflow at constrained sizes.

Reproduction Steps

1. Launch the Goose2 desktop app.
2. Open Settings from the sidebar.
3. Resize the app toward its smallest allowed size.
4. Confirm the window stops at 800x600 and the settings modal remains clear of native window controls.
5. Confirm settings navigation/content remains usable instead of clipping or overlapping.

Screenshots/Demos
Manual visual validation was performed locally; the reporter confirmed the updated behavior works well.

Verification

• jq empty src-tauri/tauri.conf.json
• pnpm exec biome check src/features/settings/ui/SettingsModal.tsx
• pnpm build
• sq agents review --intent "Constrain Goose2 desktop window minimum size and make the settings modal fit within smaller viewports"
• Pre-push gate: pnpm exec biome format ., cargo fmt --check, cargo clippy -- -D warnings, pnpm test, pnpm check, pnpm build, cargo check

[wesbillman]

BEFORE:

AFTER:

[kalvinnchau]

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