fix(review-evasion): bounded retry + audit visibility for every one-shot close's explanation comment

[JSONbored]

Summary

Round-2 audit fix (#8802): all 7 one-shot close-enforcement guards posted the contributor's only explanation via createIssueComment(...).catch(() => undefined) — a transient failure left a permanently closed PR with no visible reason and nothing ever backfilled it.

Changes

• postCloseExplanation (exported, review-evasion.ts): bounded in-handler retry — three spaced attempts (0/400/1600ms) — still fail-safe toward the close itself; exhaustion emits a level:error close_explanation_post_failed log (reaches the Sentry forwarder).
• All 7 guards route through it, and each guard's audit row now records explanationPosted: true / false / null (repo opted out of the comment — the five settings-gated sites hoist a tri-state so opt-out is distinguishable from delivery failure). An operator can now enumerate any unexplained close straight from audit_events.
• Deliberate scope call (the issue offered retry OR a backfill sweep): the sweep needs the explanation body persisted, marker-detection, and a new always-on cron surface — real machinery that's only worth building if retry residue proves nonzero. The audit field added here is exactly the evidence for that follow-up decision; noted on the issue.

Test plan

• npm run typecheck — clean
• New helper suite (fake timers): first-try success, retry-through-transients, all-fail → false + loud residue with the exact event shape, delay-ladder pin
• Guards suite extended: the draft-dodge success path asserts explanationPosted: true in the audit metadata — 226/226 + queue-2 green
• Every changed line (21 hunks, script-verified against the diff): 0 uncovered statements/branches

Closes #8802

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

❌ 3 Tests Failed:

Tests completed	Failed	Passed	Skipped
21263	3	21260	21

View the top 3 failed test(s) by shortest run time

test/unit/queue.test.ts > queue processors > linked-issue hard-rule violation persistence (#linked-issue-hard-rule-persistence) > REGRESSION (live-issue-state-change-before-re-evaluation): Pass 1 flags a real violation; Pass 2's live re-parse re-evaluates the SAME issue as clean (assignee removed) but the persisted violation still closes the PR

Stack Traces | 0.234s run time

AssertionError: expected 'error' to be 'completed' // Object.is equality

Expected: "completed"
Received: "error"

 ❯ test/unit/queue.test.ts:2843:32

test/unit/queue-2.test.ts > queue processors > #4603: the SAME sub-floor defect one-shot-closes when aiReviewLowConfidenceDisposition is explicitly one_shot

Stack Traces | 0.35s run time

AssertionError: expected 'error' to be 'completed' // Object.is equality

Expected: "completed"
Received: "error"

 ❯ test/unit/queue-2.test.ts:361:28

test/unit/queue.test.ts > queue processors > linked-issue hard-rule violation persistence (#linked-issue-hard-rule-persistence) > REGRESSION (body-edit-during-grace-window): Pass 1 flags a real owner-assigned violation; Pass 2's live re-parse finds NO linked issues (body edited) but the persisted violation still closes the PR

Stack Traces | 0.424s run time

AssertionError: expected 'error' to be 'completed' // Object.is equality

Expected: "completed"
Received: "error"

 ❯ test/unit/queue.test.ts:2798:32

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