maintainer: wire calibration accuracy into the live auto-tune circuit-breaker for miner-originated PRs

[JSONbored]

src/review/auto-tune.ts already implements the ONE tuning action considered safe to take unattended: when computeGateEval's merge precision drops below a floor for a project, the system self-tightens (sets a hold-only flag) and alerts a human — it only ever gets MORE cautious. This issue extends that existing live enforcement surface to also consider MINER-originated PRs as a distinguishable population (via the source-scoping already present on computeGateEval), so a miner fleet whose self-review accuracy degrades trips the SAME existing safety breaker independently of the maintainer's own review-stack accuracy — without ever loosening anything automatically.

This directly extends the live gate-adjacent enforcement chokepoint itself (the auto-tune breaker), so it is maintainer-only per the safety tier, even though the breaker's philosophy (self-tightening only) is already established.

Deliverables

• Extend the auto-tune breaker invocation to run a source-scoped computeGateEval pass for miner-originated predictions (using the existing source?: string filter) in addition to the existing unscoped pass
• A distinct hold-only flag scope for "miner-originated PRs from this project" so tightening miner traffic does not blanket-penalize human-submitted PRs to the same repo
• Preserve every existing invariant: forward-measured only, self-tightening only (never auto-loosens), human-clearable
• Regression tests proving the new miner-scoped breaker fires independently of the existing unscoped one, and that clearing one flag does not clear the other

References

• src/review/auto-tune.ts — the existing circuit-breaker this extends; read its full "only ever more cautious, forward-measured, human clears it" contract before touching
• src/review/parity.ts (301 lines) — computeGateEval's existing source?: string scoping parameter this reuses
• src/review/outcomes-wire.ts (536 lines) — runSelfTuneBreaker, the existing invocation site this issue extends

[linear-code]

JSO-2448