Complete the frontend Tailwind migration

[tella-butler]

Summary

• replace the monolithic authored global.css surface with Tailwind utilities plus a focused foundation-adapters.css compatibility layer
• compile and validate the real minified Tailwind sheet consistently in production, frontend development, CI, and the product demo
• fail closed on invalid CSS builds while preserving the last-known-good development sheet and xterm fallback
• preserve current Composer, sidebar, transcript, split-preview, accessibility, and responsive behavior from main

This supersedes the closed migration PR #84 and was rebuilt on current main rather than reviving its stale application code.

Verification

• bun run typecheck
• bun run frontend:check
• production buildFrontend()
• bun run website:build
• git diff --check origin/main...HEAD
• authenticated desktop and 390x844 mobile browser smoke tests; no horizontal overflow
• bun test: 1,424 passed; the worktree-only TUI test could not resolve @opentui/react/test-utils, while that same test passes from main (20/20)

[tella-butler]

🤖 Michael review · request changes · confidence 3/5

Safe once the P1 below is fixed. The production build, fail-closed validation, CI gate, and standalone frontend-dev compiler path are coherent, but the documented built-in dev mode now serves the application without any stylesheet.
1 inline comment below.

💡 Labels: os-auto-fix — I fix these and push until CI passes · os-adversarial — deeper two-pass review · os-simplify — quality cleanup pass.
_{Reviewed f64b4ef · GPT-5.6 Sol · earlier reviews collapse above · open session}

🔁 Not merge-ready and no live session owns this branch — add the os-auto-fix label and I'll fix the findings automatically.

[tella-butler]

Michael review · f64b4ef

[tella-butler]

🔴 P1 — Keep CSS available in the documented OPENSESSION_DEV mode

Removing this import leaves OPENSESSION_DEV=1 bun opensession.ts with no stylesheet at all. That remains a documented mode (docs/setup/install.md:137), and its spaEntry directly serves the Bun HTML import while frontend is null; unlike scripts/frontend-dev.ts, this path neither injects /tailwind-dev.css nor enables the hashed CSS asset route. The concrete result is that launching the server with OPENSESSION_DEV=1 loads the React application using only browser defaults, so the migrated layout and controls are effectively unusable. Reuse compileTailwindCss() in the built-in dev path and inject/serve that sheet, or retire this mode and its documentation as part of the same change.

[soutar]

I did not apply this to the stale branch. Current main already addresses the dev-mode stylesheet gap in e98509f, and the Tailwind migration itself subsequently completed on main in e345c45. A current-main merge produces 86 conflicts, largely because the frontend moved under packages/ after this branch diverged; resolving those by reviving this branch would risk restoring removed legacy CSS and superseded UI. This PR is therefore obsolete rather than safely convergent.