feature(review): surface the per-(project, ruleCode) gate-accuracy breakdown computeRuleGateEval already computes

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⚠️ Definition of Done: this issue must be completed in full, in a single PR. Do not split this
work across multiple PRs, and do not defer any Deliverable below to a follow-up issue. A PR that
satisfies only some of the Deliverables, stubs a required test, or leaves a checkbox
partially-done does NOT resolve this issue and will be closed.

Context

src/review/rule-gate-eval.ts:162's module header describes two views: one keyed by (project, ruleCode), and a blended counterpart keyed by ruleCode alone. The blended one, computeBlendedRuleGateEval, is fully wired into both src/review/outcomes-wire.ts (auto-tune breaker) and src/services/operator-dashboard.ts. Its sibling computeRuleGateEval -- the finer-grained "which rule is broken on which repo" view -- has zero consumers anywhere except test/unit/rule-gate-eval.test.ts.

Requirements

Add a route (or a new operator-dashboard field, following the existing pattern used for the blended view) that surfaces computeRuleGateEval's per-project rows, so the finer-grained view is actually reachable by an operator.

Deliverables

• A new route or dashboard field exposes computeRuleGateEval's per-(project, ruleCode) rows
• A test exercising the new route/field end-to-end, asserting it returns the finer-grained per-project breakdown, not just the already-wired blended view

All of the above Deliverables are required in the same PR unless the deliverable text itself states otherwise.

Test Coverage Requirements

src/** -- 99%+ patch coverage, branch-counted, on the new route/field.

Expected Outcome

An operator can see which specific rule is broken on which specific repo, not only the blended cross-repo view, closing a gap between what's computed and what's surfaced.

Links & Resources

• src/review/rule-gate-eval.ts:162
• src/review/outcomes-wire.ts
• src/services/operator-dashboard.ts
• test/unit/rule-gate-eval.test.ts

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JSO-6185