feat(newos4): R5 stale-artefact rule + dashboard queues a decision once

Feedback queue triage 2026-11-02: 23 reports, 22 decided, 1 open -- and the open
one (RPT-20261029-115241, "[Terminal] Error in ShellModule.test: {\"silent\":true}")
was already fixed in v4.6.135 (4472c81, modules/core/terminal.js:1966) yet could
never be cleared by automation.

Root cause: identifiers() keeps only generic class names (Terminal, ShellModule),
both of which necessarily stay in the code, so R2 (every identifier absent) cannot
fire; R4 needs a stack and this report has none. A stack-less
"Class.method: {json}" console.error whose emitter gets *guarded* -- rather than
deleted -- therefore sits "awaiting decision" forever.

- newos4-feedback-autoreview.py: new R5 stale artefact -- auto report, no stack,
  every error count <= 1, and nothing newer than STALE_DAYS=5 in
  data/debug/errors.json -> resolve with the measured quiet_days as evidence.
  New --errors <path> knob so the rule can be run against fixtures.
  RED (pristine copy): "nothing provable (1 left for the operator)"
  GREEN (aged fixture): "resolve ... quiet 5.3d -- reopen if it recurs"
  NEG (live store 4.3d, and a report with count 21): both still refuse.
- admin/feedback.html: markDecided() patches the local snapshot, so a queued
  decision leaves the default "Awaiting only" list immediately instead of after
  the 10-minute sync rebuild. Measured cause of 3x approve on one plan in 3 min
  (10-30 16:03/16:05/16:05) and 6 items with duplicate rows.
- AGENTS.md: documents R5 and the fixture knob (also carries the already-live
  2026-11-02 cookie-notice paragraph that was pending in the tree).

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