feat(pr-fix): reactivate on fresh feedback with bounded reconciliation #1253

Why

Fresh actionable feedback must not remain stranded behind an earlier FIXED, operational PARKED, or structured WAITING_EXTERNAL disposition. This is the policy/execution half of design #1244, after the evidence/fencing and external-dependency prerequisites.

Implementation

• Reuse authoritative per-generation freshness/attempt-snapshot decisions from #1249 and the structured dependency contract from #1250.
• Implement one bounded, idempotent evaluateRecovery transition used both by event-driven enqueue and periodic authoritative re-read. Preserve existing in-flight worker ownership; a new observation during execution is recorded for post-dispatch settlement, not a second active hand-out.
• Reactivate FIXED on new actionable evidence, budget-available operational PARKED after allowed cooldown, and a structured WAITING_EXTERNAL when its dependency trigger fires or a fresh independent review arrives. New actionable feedback opens a charged attempt; normal external-dependency rechecks remain uncharged.
• Never override BLOCKED human decisions, maintainer holds, infra/security fail-closed parks, max-attempt/max-reclaim exhausted parks, or merged/closed/archived PRs. Record newer evidence and surface a stale-disposition flag rather than silently dropping it.
• Fence all reactivation, settlement and terminal reap transitions on live generation/snapshot and owner acknowledgements; old workers cannot settle fresh work. Preserve immutable PrFixHistory, cap/cooldown defaults, and existing operator requeue escapes.
• Bounded pagination, re-read limits, retry backoff, restart-safe cursors/timestamps and audit actor/evidence metadata; no new Courier model/phase dependency.

Acceptance / negative controls

• Feedback during execution, delayed webhook first discovered after FIXED, new comment during external wait, and genuinely new feedback on budget-available operational PARKED eventually produce exactly one new generation.
• Duplicate/replayed/out-of-order reviews, previously seen persistent merge conflicts, re-read after bounded-key eviction, and resolved review threads never requeue.
• Cap exhaustion parks with operator-visible stale evidence; human hold, old-worker settlement, claim ack race and merged PR never lose ownership or reopen.
• Missed webhook repaired by periodic reconcile; parallel reconcile/event/requeue calls idempotent. Exhaustive transition-table tests corresponding to #1248 and no unbounded retry loops.

Dependencies

Blocked by #1249, #1250, and accepted design PR #1248. No auto bulk requeue of legacy waiting records.