feat: add Multi Monitor oven

[alowpoly]

Summary

• add a Codex-style Multi Monitor oven for viewing several tasks in columns
• add shared Codex App Server messaging with approvals and user-input handling
• harden loopback authorization, idempotency, durable receipts, bridge lifecycle, liveness, and draft handling
• add responsive fixed-height composers, stable task titles, retained-history disclosure, and visible focus

Verification

• full npm run verify passed before the final stylesheet-only split
• post-split dashboard build and all 255 dashboard tests passed
• terminal and console Oven audits passed
• npm run verify:package passed with the exact 262-file payload
• painted three-column browser check passed with zero console errors