fix: [ENG-2851] reformat ternary, add e2e restore-on-reject guardrail, signal meta downgrade

Round 2 review follow-ups:

1. agent-process.ts curate-html-direct result: my prior commit claimed to
   split the JSON-stringify ternary into an if/else, but lint:fix's
   `unicorn/prefer-ternary` reverted it. Reformat as a multi-line ternary
   with no trailing semicolon and proper one-line-per-branch indentation
   — satisfies the lint rule AND matches the surrounding file style.

2. test/unit/infra/transport/handlers/review-handler-reject-restore.test.ts:
   new e2e contract test that drives the full curate-UPDATE → reject cycle
   through `ReviewHandler.handleDecideTask` with REAL stores rooted at a
   tmpdir. Proves the *sufficient* condition for restore-on-reject — the
   prior unit tests only proved the necessary condition (backup file
   exists with the right bytes). If the keying ever drifts between the
   curate side and the handler side, this test fails and production no
   longer silently destroys content.

3. shared/transport/curate-html-content.ts: emit a single stderr line
   when a meta payload arrives but fails zod validation (downgraded to
   undefined). Guarded on `BRV_QUEUE_TRACE` so production stays quiet;
   operators diagnosing a forward-incompat field-rename now have a
   grep-able signal instead of a silent loss of review surfacing.