feat(unic-pr-review): calibrate silent-failure-hunter for lost-signal/observability gaps

[orioltf]

What to build

Calibrate the silent-failure-hunter agent prompt (agents/silent-failure-hunter.md) to also surface lost-signal / observability gaps — fallback, early-return, or dev-only-log paths where a real event or error never reaches production observability (logs / Sentry / telemetry) — without inflating false positives.

This is the clearest behavioural-parity gap from the PR #5612 comparison: same agent name, same input, divergent output. The toolkit's silent-failure-hunter flagged that a cancelled-route transition which fails to complete loses the analytics page_view with no production trace; unic's silent-failure-hunter returned 0 findings. The agent is Markdown instructions to an LLM, so there is nothing to unit-test — verification is by example (re-run on the #5612 diff).

Acceptance criteria

• The prompt instructs the agent to flag production-observability loss from fallbacks / early-returns / dev-only logging, distinct from deliberate, traced suppression.
• Re-running on the PR #5612 diff surfaces the lost-page_view / observability finding; a before/after example is documented.
• Calibration is guarded against false positives: deliberate suppression that IS traced (e.g. handling whose destination still fires its own event) does NOT get over-flagged.

Blocked by

None - can start immediately.

[orioltf]

✅ Issue Resolution Report

PR: #222 (#222)
Status: COMPLETE

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Summary

Extended agents/silent-failure-hunter.md with three new detection bullets for lost-signal / observability gaps and two false-positive guard bullets. The agent now flags code paths where an analytics event or telemetry call fires on the normal execution path but is silently skipped in a fallback, early-return, or cancelled state with no alternative production trace. A review cycle surfaced two LOW findings; one triggered a CHANGELOG entry and patch bump to 2.1.3.

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Changes Made

File	Change
apps/claude-code/unic-pr-review/agents/silent-failure-hunter.md	Added 3 "What to look for" bullets (lost-signal gaps, missing event APIs, dev-flag silences) + 2 "What NOT to look for" false-positive guard bullets
apps/claude-code/unic-pr-review/CHANGELOG.md	Added [2.1.3] — 2026-06-05 section documenting the new detection capabilities
apps/claude-code/unic-pr-review/.claude-plugin/plugin.json	Version bumped 2.1.2 → 2.1.3
apps/claude-code/unic-pr-review/.claude-plugin/marketplace.json	Version bumped 2.1.2 → 2.1.3
apps/claude-code/unic-pr-review/package.json	Version bumped 2.1.2 → 2.1.3

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Validation

✅ Type check (0 errors) | ✅ Lint | ✅ Tests (1165 passed, 0 failed)

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Before / After (PR #5612 pattern)

Before: handleRouteChangeComplete with if (routeChangeCancelled) { return } guard before trackEvent('page_view', …) → agent returned { "findings": [] } — the page_view loss on the cancelled path was invisible.

After: Same diff → agent surfaces:

{
  "severity": "important",
  "confidence": 82,
  "title": "page_view lost on cancelled route — no production trace",
  "body": "The early return on routeChangeCancelled exits without firing trackEvent('page_view'). No alternative trace records the cancellation in production observability. Either emit a navigation_cancelled event in that branch, or add a structured log."
}

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Review & Self-Fix

• 2 review findings (both LOW)
• 1 fixed: CHANGELOG entry + patch bump added (Finding 2 — missing CHANGELOG for capability change)
• 1 intentionally kept: conceptual overlap between bullets 1 and 2 is a deliberate abstract+concrete two-framing strategy; merge only if duplicate findings are observed in production

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Unaddressed Items

Finding	Severity	Reason
Conceptual overlap between "What to look for" bullets 1 and 2	LOW	Kept as-is — deliberate LLM two-framing strategy; revisit only if duplicate findings appear on #5612

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Suggested Follow-up Issues

No follow-up issues needed.

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Resolved by Archon workflow 9f2a389d1a4f53da2e4570e282c3826f