fix(projects): restore project deletion

[chicoxyzzy]

Summary

• route Cairnline-only project deletion directly through the authoritative delete and rollback path instead of requiring absent legacy stores
• update the Cairnline pin so durable handoff command receipts are included in project cleanup
• keep API failures and ownership blockers inside the delete dialog with exact operator guidance, retry, and focus recovery
• cover state ownership, both project surfaces, narrow browser behavior, and production-shaped backend wiring

Root cause

Production replacement mode intentionally has no native portable project stores, but deletion tried to load a native snapshot before reaching Cairnline. That returned projects store is required for every delete. Projects with durable handoff receipts also needed the merged Cairnline cascade fix from hecatehq/cairnline#85.

Verification

• copied the desktop SQLite databases to an isolated data directory; the patched binary deleted the copied existing project with HTTP 200 and a follow-up GET returned 404
• bun run typecheck
• bun run lint
• bun run format:check
• bun run test (107 files, 2,415 tests)
• targeted Playwright deletion failure/retry test at desktop and 390px widths
• GOCACHE=/Users/chicoxyzzy/dev/hecate/.gocache go test -race -timeout 10m ./...
• independent backend contract review: no findings
• independent UX/accessibility review: findings fixed, final review clean