fix(theme): adapt project context modal to light mode

[vickioo]

Summary

• Updates the Project Context edit modal to use the shared semantic theme tokens instead of hard-coded dark colors.
• Aligns the modal backdrop, surface, borders, text, textarea, and action buttons with the existing light/dark appearance system.

Validation

• npm run verify:theme-tokens passes with 126 referenced tokens.
• npm run build passes; only the existing Vite large chunk / dynamic import warnings remain.

[vickioo]

Small follow-up after the light-theme merge: this adapts the Project Context edit modal to the same semantic theme tokens used by the other modals. It is a single-file change and locally passed npm run verify:theme-tokens plus npm run build.

[vickioo]

Local app validation passed as well: I rebuilt and launched the macOS dev app with this patch, switched through the light UI path, and verified the Project Edit context… modal now matches the shared light/dark token system.