feat: add directory-scoped auto permissions

[leoncheng57]

Summary

• add a volatile, directory-scoped BFF auto-permission coordinator and strict GET/PATCH API
• reconcile pending requests and reply once to permission.asked while preserving manual retry on failures
• clear durable auto-reply failures after permission.replied or reconciliation removes the request
• suppress permission and parked-permission notifications while enabled, without affecting questions
• add prominent enabled-state warnings and compact off-state controls on Hub and Conversation
• widen permission request typing and document the safety contract
• integrate current main, preserving issue bug: Build sessions can lose shell and edit tools after a mode switch #15 policy activation, recent sessions, appearance, and PR feat: make full sessions reliable on mobile #17 mobile/full-session behavior
• constrain transcript stacking so auto status and the expanded mobile transcript cannot intercept composer controls

Verification

• npm run typecheck
• npm test (17 files, 161 tests passed)
• npm run build
• lockf -k /tmp/custom-dca-opencode-e2e.lock npm run test:e2e (121 tests passed)
• git diff --check

Safety caveats

• Auto permissions can approve arbitrary asked shell commands, external-directory access, and repeated doom-loop requests for every session in the enabled directory.
• State is intentionally BFF-memory-only, defaults off, and resets off on restart.
• The coordinator only sends reply: "once"; it never mutates OpenCode config/session policy, sends always, or answers questions.
• Auto mode does not modify Plan/Build policy. The merged issue bug: Build sessions can lose shell and edit tools after a mode switch #15 implementation activates durable session policy before each prompt and restores Build from resolved agent policy in a separate serialized critical section.
• Permission and parked notifications are suppressed while enabled; auto-reply failures remain visible in the UI and leave the manual permission card retryable.