recovery: document MR-847 ship across all reference docs (Phase 10)

Update the doc surface to reflect MR-847 having shipped end to end —
sidecar protocol, classifier, all-or-nothing decision tree, roll-forward
via ManifestBatchPublisher, roll-back via Dataset::restore with
fragment-set short-circuit, audit trail in
_graph_commit_recoveries.lance, OpenMode::{ReadWrite, ReadOnly}, and
the four migrated writers all carrying sidecars across Phase B → Phase C.

- docs/invariants.md §VI.23: change from "upheld at the writer-trait
  surface for inserts/updates/etc., per-table commit_staged → manifest
  publish window remains" to "upheld at the writer-trait surface AND
  across process boundaries". The MR-847 sweep closes the residual on
  the next Omnigraph::open. The "continuous in-process" property
  (no ExpectedVersionMismatch surfacing to subsequent writers between
  Phase B failure and process restart) is honest follow-up at MR-856.

- docs/runs.md: replace "Finalize → publisher residual" section with
  "Open-time recovery sweep (MR-847)" — describes the sidecar protocol
  lifecycle (Phases A-D), the sweep's classifier + decision dispatch,
  the audit trail, and the operator-facing query
  (omnigraph commit list --filter actor=omnigraph:recovery).

- AGENTS.md capability matrix "Atomic single-dataset commits" row:
  drop the "Layer (3) is not yet shipped — tracked in MR-847" caveat;
  describe the three layers as all shipping; reference MR-856 for the
  background-reconciler follow-up.

- docs/storage.md: add _graph_commit_recoveries.lance and
  __recovery/{ulid}.json to the on-disk layout (mermaid + prose).

- docs/branches-commits.md: new "Recovery audit trail (MR-847)"
  subsection describing the join from
  _graph_commits.lance:actor_id="omnigraph:recovery" to
  _graph_commit_recoveries.lance:graph_commit_id for operator
  post-mortem.

- docs/maintenance.md: note the MR-847 recovery floor on cleanup —
  --keep < 3 may garbage-collect Lance versions the recovery sweep
  needs as a rollback target. Default --keep 10 is safe.

- docs/testing.md: add tests/recovery.rs to the engine integration-test
  table; expand the failpoints.rs row to mention the four MR-847
  per-writer Phase B → recovery integration tests.

- .context/mr-847-design.md: prepend a "Status: DONE" stanza listing
  every commit hash + scope across phases 1-10.

AGENTS.md ↔ docs/ cross-link check passes (26 links, 26 docs).
Full workspace test sweep passes with --features failpoints (361 tests
across 20 binaries).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/invariants.md

@@ -105,13 +105,13 @@ These are user-visible commitments. They state what the engine guarantees and wh
 Specific defaults (timeout values, memory caps, TTL windows) are *configuration*, not invariants — see [docs/constants.md](constants.md) and per-deployment configuration. The invariant is that bounds and contracts exist, not their numerical values.
 
 23. **Atomicity is per-query.** Every `.gq` query is atomic — multi-statement mutations are all-or-nothing via the substrate's atomic-commit primitive. No cross-query `BEGIN`/`COMMIT`; branches and merges fill that role for agent workflows.
-    *Status: upheld at the writer-trait surface for inserts / updates / scalar-index builds / merge_insert / overwrite after MR-793 PR #70 — the sealed `TableStorage` trait routes those through `stage_*` + `commit_staged`, so a Phase A failure (between writing fragments and committing) leaves no Lance-HEAD drift on touched tables. **Per-table commit_staged → manifest publish window remains** — a failure between commits across multiple touched tables can leave drift on the partially-committed tables. Lance has no multi-dataset atomic commit primitive; closing this requires the recovery-on-open reconciler tracked in MR-847. Additionally, two writer paths still inline-commit pending upstream Lance work: `delete_where` (lance-format/lance#6658) and `create_vector_index` (lance-format/lance#6666).*
+    *Status: upheld at the writer-trait surface AND across process boundaries after MR-847 — the sealed `TableStorage` trait routes inserts / updates / scalar-index builds / merge_insert / overwrite through `stage_*` + `commit_staged` (Phase A is drift-free), and the open-time recovery sweep in `db/manifest/recovery.rs` (sidecars at `__recovery/{ulid}.json` written by `MutationStaging::finalize`, `schema_apply`, `branch_merge`, `ensure_indices`) closes the per-table commit_staged → manifest publish residual on the next `Omnigraph::open`. The "Lance HEAD ahead of `__manifest`" drift class is unreachable for op-execution failures and recoverable across process boundaries for finalize→publisher failures. Continuous in-process recovery (no restart required between Phase B failure and recovery) arrives with MR-856 (background recovery reconciler). Two writer paths still inline-commit pending upstream Lance work: `delete_where` (lance-format/lance#6658) and `create_vector_index` (lance-format/lance#6666).*
 
 24. **Schema integrity is strict at commit.** Type validation, required-field presence (auto-filled from `@default` if declared), uniqueness across batches and versions, and referential integrity — all enforced before commit succeeds. Per-write softening flags are opt-in, never default.
     *Status: aspirational — referential integrity at scale requires SIP-backed cross-table validation; not yet implemented. Cross-batch / cross-version uniqueness tracked in MR-714.*
 
 25. **Isolation: per-query snapshot; read-your-writes within and across queries in a session.** Each query reads from one consistent manifest version. Within a multi-statement mutation, the read subplan inside each write operator sees the writes from earlier statements. Across queries in a session, reads always resolve the latest manifest version — no reader pinning to older snapshots.
-    *Status: upheld for inserts/updates after MR-794 step 2+ — `MutationStaging`'s in-memory accumulator + `TableStore::scan_with_pending` (DataFusion `MemTable` union with the committed Lance scan, with merge-shadow semantics for chained updates) implements read-your-writes within a multi-statement mutation. Delete-touching mutations are limited to delete-only by parse-time D₂; closing the within-query RYW gap for deletes requires Lance's two-phase delete API (tracked: MR-793 / Lance-upstream lance-format/lance#6658). The "Lance HEAD ahead of `__manifest`" drift class is unreachable for op-execution failures (the partial-failure test pins this), but a narrowed residual remains at the finalize→publisher boundary because Lance has no multi-dataset commit primitive — see [docs/runs.md](runs.md) "Finalize → publisher residual".*
+    *Status: upheld for inserts/updates after MR-794 step 2+ — `MutationStaging`'s in-memory accumulator + `TableStore::scan_with_pending` (DataFusion `MemTable` union with the committed Lance scan, with merge-shadow semantics for chained updates) implements read-your-writes within a multi-statement mutation. Delete-touching mutations are limited to delete-only by parse-time D₂; closing the within-query RYW gap for deletes requires Lance's two-phase delete API (tracked: MR-793 / Lance-upstream lance-format/lance#6658). The "Lance HEAD ahead of `__manifest`" drift class is unreachable for op-execution failures (the partial-failure test pins this), and the narrower finalize→publisher residual is closed across one open cycle by the MR-847 recovery sweep — see [docs/runs.md](runs.md) "Open-time recovery sweep".*
 
 26. **Durability before acknowledgement.** Commit returns only after the substrate has confirmed durable persistence. No "fast" or "fire-and-forget" durability levels.