PROC-2b · Triage/SLA the ~142–155 stuck-active tasks

> Item derived from the fact-checking cycle analysis (**2026-07-03, v2**). Split from PROC-2 (#2500).

### Finding (evidence)
The **~142–155 stuck-active** tasks (have content, idle **~226–235 days**; in `main` only, ~108 → ~70 days). This is the **real backlog** to drain.

### Action
Expiry/reassignment policy, WIP limit and/or queue SLA. The technical "how" is TECH-4 (SLA + auto-owner).

### Impact
The genuine backlog is drained or bounded; live WIP.

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- **Priority:** 🔴 High
- **Dependencies:** INST-4 (#2494) to measure; TECH-4 for the mechanism.
- **Parent:** #2500 · **Epic:** #2490