Add config-as-code coverage for the parityAudit feature

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Part of #4092.

Problem

isParityAuditEnabled (src/review/parity-wire.ts) is not migrated onto the existing per-repo feature-activation mechanism (src/review/feature-activation.ts; NOT a new resolver to build, see #4092's corrected state) — purely GITTENSORY_REVIEW_PARITY_AUDIT + the shared allowlist today.

Fix

• Add "parityAudit" to CONVERGED_FEATURE_KEYS + FEATURE_GLOBAL_FLAG (mapping to isParityAuditEnabled).
• Migrate parityAudit's real call site(s) to convergedFeatureActive/resolveConvergedFeature.
• .gittensory.yml.example + config/examples/gittensory.full.yml document the new features.parityAudit key.

Deliverables

• parityAudit added to CONVERGED_FEATURE_KEYS + FEATURE_GLOBAL_FLAG
• Real call site(s) migrated
• Tests mirroring the existing feature-activation test pattern
• Docs updated

Expected outcome

An operator can turn the reviewbot-parity audit on/off per-repo purely through config.

Effort

S — mechanical migration onto an existing, proven mechanism.

[linear-code]

JSO-3155

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Closing as investigated, no code change warranted — the issue's premise doesn't hold on direct inspection.

The claim: isParityAuditEnabled is gated by "GITTENSORY_REVIEW_PARITY_AUDIT + the shared allowlist today," so migrating it onto CONVERGED_FEATURE_KEYS/resolveConvergedFeature (mirroring rag/reputation/unifiedComment/safety/grounding) would be mechanical.

What's actually there: there is no allowlist involved anywhere in this feature.

• src/review/parity-wire.ts:144 — the only gate is if (!isSelfHostedReviewRuntime(env) && !isParityAuditEnabled(env)) return;. No isConvergenceRepoAllowed call in this file, its call site (processors.ts gate-evaluation finalize path), or the GET /v1/internal/parity endpoint (src/api/routes.ts, if (!isParityAuditEnabled(c.env)) return c.json({error:"not_found"},404)).
• CONVERGED_FEATURE_KEYS (packages/gittensory-engine/src/focus-manifest.ts) is ["rag", "reputation", "unifiedComment", "safety", "grounding"] — the 5 keys that GITTENSORY_REVIEW_REPOS's own doc comment in env.d.ts explicitly enumerates as the allowlist's scope. parityAudit was never among them.
• GITTENSORY_REVIEW_PARITY_AUDIT's own doc comment in env.d.ts describes it as a "RECORD-ONLY SHADOW mode — recording changes NO review behavior," with no allowlist mention.

Why adding a per-repo override would be a regression, not a fix, mirrors #4106's reasoning:

• On self-host, the recorder writes unconditionally regardless of the flag (!isSelfHostedReviewRuntime(env) && !isParityAuditEnabled(env)) — exportOrbBatch's fleet telemetry INNER JOINs gate_decision to pr_outcome and needs this row to exist. A per-repo features.parityAudit: false override would silently break that self-host telemetry contract for the opted-out repo.
• On the cloud worker, a per-repo true override would let any repo spend the operator's shared Cloudflare D1 write budget on its own say-so — the same "spend the shared budget on its own say-so" concern Investigate + design config-as-code for ops / sweep_watchdog / pr_reconciliation #4106 used to reject folding ops/sweep_watchdog/pr_reconciliation onto this resolver.
• The purpose of parity recording (cutover-readiness comparison across the fleet) is fleet-wide, not a review behavior the reviewed repo itself opts into or benefits from — same shape as Investigate + design config-as-code for the GITTENSORY_REVIEW_DRAFT public draft-submission flow #4107's conclusion for the draft-submission flow.

Net: GITTENSORY_REVIEW_PARITY_AUDIT correctly stays a deploy-wide flag with no per-repo axis. If a genuine self-host opt-out is ever needed, it would have to be a narrow, self-host-only exclusion — not a bidirectional resolveConvergedFeature override — which is a different, smaller issue than what's filed here.