…dit (#646)

Fixes identified during full-stack bug hunt. Refs #643 #644 #645.

## app

- terminal.tsx: use strict equality (===) for the Enter key check; add .catch() to document.fonts.ready so a font-loading rejection cannot become unhandled.
- layout.tsx: add .catch() handlers to the three dynamic imports (provider, server, directory dialogs) so a chunk-load failure does not surface as an unhandled rejection.
- global-sync.tsx: add .catch() to the projectInit promise; guard the requestAnimationFrame callback with `if (!active) return` so it cannot schedule work after cleanup tore the owner down.
- sync.tsx: call clearOptimistic(directory, sessionID) when dropping sessions, so the optimistic Map no longer leaks entries for sessions that disappear.

## opencode

- tool/agent.ts: add a default case to the part.status switch so a new status value cannot leave header and body undefined.
- control-plane/workspace.ts: wrap the parseSSE call in try/catch so a malformed SSE event does not terminate the workspace sync loop.
- tool/apply_patch.ts: replace `(error as any)` in notFound() with a proper `Record<string, unknown>` narrowing.

## Rescue rebase notes

The PR originally bundled three additional commits that did not survive review and were dropped or partially reverted on rebase:

- A dead-code cleanup commit that was equivalently merged via #641 (with reviewer fixups for tool-info.ts and session-link.ts). Keeping it here would have re-introduced four TS2393 duplicate-definition errors on the worktree helpers; dropping the commit cleared them.
- A separate input-validation commit (SQL prefix allowlist, http(s) URL guard, config-path scoping, parseInt radix/NaN fallback). The DB connection is already readonly, fetch() already rejects non-http(s) schemes, downstream code already tolerates NaN, and the config-path rule is a user-visible behavioral break with no concrete threat model — dropped, can revisit any item individually in a follow-up.
- One line of the original race/error commit removed an `as any[]` cast in provider/transform.ts on the assumption that Array.isArray narrowed sufficiently. It does not: TS narrows the system-message branch union to `never`, so the cast is still required. Restored.

## Verification

- packages/ui typecheck clean.
- packages/app typecheck clean.
- packages/opencode typecheck clean.
- CI green across typecheck, unit-app, unit-desktop, unit-opencode, smoke-macos-arm64, e2e-artifacts, perf-probe-baseline, lint, analyze-js-ts, CodeQL.
- Both bot review threads resolved (Gemini manual, CodeRabbit auto-detected).