perf(worktrees): skip unchanged projection updates and evidence replay

[Juliusolsson05]

Problem

Quiet sessions receive new worktree projection identities for identical Git data, and unrelated transcript batches replay up to 500 retained records on the renderer thread.

Change

• Preserve canonical state/context references when values agree.
• Reuse catalog content identity independently of freshness.
• Cache replay by cwd, authoritative baseline, evidence generation and catalog identity.
• Keep catalog-ready callbacks: unchanged catalogs must still correct externally replaced stale history.
• No lifecycle, readiness, terminal, dependency or persisted-schema changes. No migration required.

Verification

Seven new invalidation/identity regression tests, including actual retained-record read counts. Four tests failed on unchanged production code before the fix. Existing recorded attribution tests remain green, including stale-hydration accounting reversal.

24 focused unit tests, 2 worktree UI renderer tests, full typecheck, test contract and five-fixture privacy gate passed.
Full local unit suite: 2138 passed, one existing missing-private-session corpus failure, reproduced identically on unchanged main (Refs #684/#669/#641). No skips or weakened assertions. Both current CI gates passed on cccae6e (quality-gate and minimum-node-fixture-gate, run 33957522009); the review-fix head 29e2dc8 re-triggers CI.

Before/after measurement

Reproducible sanitized-fixture script: scripts/benchmark-worktree-reconciliation.mts.
200 unrelated batches with 500 retained records: median 2.118166 ms to 0.000333 ms; p95 2.476792 ms to 0.000375 ms; unnecessary identity changes 200 to zero. Isolated synchronous work only, not an app-wide typing-latency claim.

Review

Two independent orchestration reviewers approved cccae6e with no correctness defects: invalidation keys (cwd, baseline identity, evidence revision, catalog identity), retained identity, replay avoidance, and the accounting-reversal path were all verified. Final head 29e2dc8 only renames the replay-cache coverage file to LiveWorktreeReconciler.invalidation.test.ts — it protects identity/invalidation contracts, not timing, and the previous .performance suffix implied a tier this repo does not define. Boundary worth knowing (recorded in #806): any checkout commit change intentionally invalidates catalog identity because sameCatalog compares head, so that cwd replays its bounded evidence window at the next refresh. A pre-existing, unrelated evidence-eviction loss (>500 relevant records buffered before the first successful Git IPC reply are folded against an empty catalog and dropped) is filed separately, not fixed here.

Boundaries / remaining work

The existing bounded full replay remains for genuine invalidations; timestamp and attribution policy are unchanged. Per-pane subscriptions #763, screen interest #762 and remaining diagnostics #767 are separate increments. No overlap with A6 #802-805. Await explicit owner approval before merge.

Fixes #806

[Juliusolsson05]

Verification update: both current CI checks passed on cccae6e (quality-gate and minimum-node-fixture-gate, run 33957522009). Local baseline-only corpus failure remains documented above. Implementation is ready for review; no merge performed or authorized.

[Juliusolsson05]

Owner authorized review, fixes, and merge of #808/#810 after final checks. Two independent reviewers have been started through Agent Code orchestration (Review A and Review B); each covers both PRs and their interaction at cccae6e / a96f00a. Current CI gates pass. Planned order: #808 first, then update #810 with resulting main and verify combined state. Merge remains gated on both review outcomes.