feat(miner-selfimprove): local prediction-ledger schema — record every predicted-gate verdict for later scoring

[JSONbored]

packages/gittensory-miner/lib/ already has two local SQLite-backed ledgers with a consistent, well-established schema/CRUD style this item should mirror:

• event-ledger.js/.d.ts — the general-purpose one: appendEvent({ type, repoFullName?, payload }) -> LedgerEntry { id, seq, type, repoFullName, payload, createdAt }, plus readEvents(filter?: { repoFullName?, since? }), resolveEventLedgerDbPath(env?), initEventLedger(dbPath?), and closeDefaultEventLedger().
• governor-ledger.js/.d.ts — the more structured, decision-shaped one: appendGovernorEvent({ eventType, repoFullName?, actionClass, decision, reason, payload? }) -> GovernorLedgerEntry { id, ts, eventType, repoFullName, actionClass, decision, reason, payload }, with the matching resolveGovernorLedgerDbPath/initGovernorLedger/readGovernorEvents/closeDefaultGovernorLedger quartet.

A prediction ledger is closer in shape to governor-ledger.js (it's recording one decision-shaped event per predicted-gate call, not an arbitrary payload) — mirror its pattern rather than event-ledger.js's.

The ledger needs to record enough about each PredictedGateVerdict (packages/gittensory-engine/src/predicted-gate.ts:43-61: conclusion, pack, readinessScore, blockers/warnings, confirmedContributor) to later score it against a realized outcome — this is exactly what computeGateEval (src/review/parity.ts:88) does server-side for the live gate, joining a gate_decision prediction row to a pr_outcome ground-truth row by target_id and MAX(created_at) (src/review/parity.ts:95-112). The miner-local ledger needs an equivalent join key (repo + PR/issue identifier, or a commit SHA) so a later scorer (the calibration dashboard item in this same batch, or #4248's wiring) can pair a locally-recorded prediction with whatever ground truth eventually becomes available (the real gate's later merge/close, once observable, or a replay-harness score).

Deliverables

• packages/gittensory-miner/lib/prediction-ledger.js (+ .d.ts) mirroring governor-ledger.js's shape: resolvePredictionLedgerDbPath(env?), initPredictionLedger(dbPath?), appendPrediction(input), readPredictions(filter?), closeDefaultPredictionLedger().
• A PredictionLedgerEntry type recording at minimum: id, ts, repoFullName, a join key (e.g. targetId/PR or issue number, headSha if available), the verdict's conclusion/pack/readinessScore, blocker/warning codes (not full free-text detail — keep rows small and stable for later diffing), and the ENGINE_VERSION that produced it (ties into the engine-parity-drift-detector item in this batch — a row should self-report which engine build made the call).
• CRUD parity with the existing ledgers: same SQLite-file resolution convention, same close() semantics, same defensive/fail-safe behavior on a missing/corrupt state dir (mirror whatever event-ledger.js/governor-ledger.js already do there).
• Follow the existing per-ledger CLI precedent (event-ledger-cli.js, governor-ledger-cli.js each wrap their own ledger module) — add a minimal prediction-ledger-cli.js for consistency if a CLI surface is added at all in this item; otherwise leave CLI wiring to a follow-up and keep this item to the storage module itself.
• Unit tests for appendPrediction/readPredictions (including the repoFullName/join-key filter), DB-path resolution, and idempotent close(), mirroring the existing ledger test patterns.

References

• packages/gittensory-miner/lib/governor-ledger.d.ts (schema/CRUD shape to mirror)
• packages/gittensory-miner/lib/event-ledger.d.ts (the more generic sibling pattern)
• packages/gittensory-miner/lib/governor-ledger-cli.js, event-ledger-cli.js (existing per-ledger CLI precedent)
• packages/gittensory-engine/src/predicted-gate.ts:43-61 (PredictedGateVerdict — the shape being recorded)
• src/review/parity.ts:88-112 (computeGateEval — the server-side join-by-target-id-and-time pattern this ledger's join key should support mirroring)
• packages/gittensory-engine/src/version.ts:4 (ENGINE_VERSION, recommended per-row provenance field)

[linear-code]

JSO-3250