Migrate data-fidelity repair from isRegistered to isInstalled

[JSONbored]

Part of #5016. Depends on #5028 (isInstalled reliability) and #5021 (backfill retarget — this dispatches that job type).

Problem

repairDataFidelity (src/queue/processors.ts:4214-4270) filters repositories.filter(isRegistered) to decide which repos' cached labels/issues/PRs get freshness-checked and repaired. This has nothing to do with subnet economics — it's cache hygiene for any repo gittensory reviews.

Current behavior

registeredRepos = repositories.filter(isRegistered) drives both the freshness-SLO report and which repos get backfill-registered-repos repair jobs dispatched.

Target

Change the filter to isInstalled. This directly matches the intent of #5021 (which retargets the underlying backfill job itself) — both should agree on the same scoping signal.

Requirements

• Freshness-SLO reporting and repair-job dispatch both scope to isInstalled repos only.
• A repo that is isRegistered=true but not installed no longer gets repair jobs dispatched for it.

Deliverables

• Updated filter in repairDataFidelity.
• Regression test mirroring feat(docs): add install site and mcp diagnostics #1's shape (installed-not-registered repo included; registered-not-installed repo excluded).
• Full local gate green, 99% patch coverage on the diff.

[linear-code]

JSO-3630