Add /feedback slash command with confirmation flow

[lezama]

Related issues

• None — small standalone addition inspired by Claude Code's /feedback.

How AI was used in this PR

Claude (Opus 4.7) drafted the code, tests, and this description. I drove the design (matching Claude Code's two-step "describe → confirm" flow shown in the screenshots that motivated the PR) and reviewed the diff.

Proposed Changes

Bring Studio AI's bug-report flow up to par with Claude Code's /feedback. Type /feedback in the chat and:

1. Describe: a free-form prompt asks "Describe the issue or feedback".
2. Review: Studio shows a "Submit Feedback / Bug Report" summary listing what will be pre-filled — your description plus environment info (platform/arch, Node version, Studio CLI version, current AI provider/model).
3. Confirm: a Submit / Cancel picker. Cancel exits cleanly. Submit opens GitHub's bug report form with summary and logs already filled in — you finish and submit on github.com.

No telemetry, no hidden submission — the user always reviews on GitHub before sending.

Files

• apps/cli/ai/slash-commands.ts — new runFeedbackSlashCommand, environment collector, URL builder, confirmation picker, and registration.
• apps/cli/ai/tests/slash-commands.test.ts — 4 new tests covering registration, the happy path (Submit), explicit Cancel, empty description, and Esc-aborts.
• apps/cli/vitest.config.ts — defines __STUDIO_CLI_VERSION__ for tests so the env block can read it under Vitest (mirrors how __IS_PACKAGED_FOR_NPM__ is handled today).

Testing Instructions

1. npm run cli:build && node apps/cli/dist/cli/main.mjs ai
2. Type /feedback and walk the flow:
   • Submit a non-empty description → confirm → browser opens GitHub's bug report with summary and logs pre-filled.
   • Submit empty description (or just whitespace) → command exits with "Feedback canceled."
   • Pick Cancel at the confirmation step → no browser, "Feedback canceled."
   • Press Esc on the description prompt → "Feedback canceled."
3. npm test -- apps/cli/ai/tests/slash-commands.test.ts — 33/33 green locally.

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?