release: v0.8.1

Version bump across all seven workspace crates + path-dep constraints,
Cargo.lock, openapi.json, and the AGENTS.md surveyed version (also
restores the RFC-process row in the topic index that was dropped during
branch juggling). Release notes: docs/releases/v0.8.1.md.

Channel note: crates.io publication is deferred for this release — the
substrate is a rev-pinned Lance pre-release (git dependency), which
published crates cannot reference. publish-crates.yml gains a
self-healing guard that skips cleanly while the pin is a git dep and
resumes automatically when the dependency returns to a registry version
(Lance 9.0.0 stable → v0.9.0); a workflow_dispatch catch-up can then
publish any skipped tag. Binaries, Homebrew, and the installer ship
normally via release.yml.

docs/releases/v0.8.1.md

@@ -0,0 +1,98 @@
+# Omnigraph v0.8.1
+
+A reliability and features release. The storage substrate moves to Lance
+9.0.0-beta.15, adopting two upstream fixes that matter for embedding-heavy
+workloads; filtered vector search now applies filters before the search;
+schema migration learns enum widening; and the query language gains
+undirected edge traversal. **The on-disk format is unchanged (internal schema
+v4)** — v0.8.0 graphs are served as-is, no rebuild.
+
+**Channel note:** this release ships as binaries, Homebrew, and the
+installer. crates.io publication is deferred for one release: the substrate
+is pinned to a Lance pre-release, which exists as a git tag rather than a
+registry version, and published crates can only reference registry versions.
+`cargo install` users can build the tag directly —
+`cargo install --git https://github.com/ModernRelay/omnigraph --tag v0.8.1 omnigraph-cli`
+— or use the installer. Registry publication resumes at v0.9.0 with Lance
+9.0.0 stable.
+
+## Highlights
+
+- **Storage substrate: Lance 9.0.0-beta.15.** The Lance team resolved two
+  issues upstream that this release adopts (lance#7480, lance#7320); both
+  could surface on embedding-heavy graphs under routine write-then-maintain
+  patterns. If you have seen filtered reads fail with a record-batch length
+  error after refresh-style updates and deletes, or keyed lookups fail after
+  `optimize` on a recently-updated table, upgrading the binary resolves both
+  — **the data on disk was always intact, and no repair step is needed.**
+  The interim vendored patch omnigraph carried for the first issue is
+  retired now that the fix is upstream. The bump was validated against a
+  full review of the upstream changes (382 commits) plus the complete local
+  and CI test matrix, including S3 integration.
+
+- **Filtered vector search returns what it should.** Combining a `match`
+  filter with `nearest()` (or `bm25()`) previously applied the filter after
+  the ANN top-k, so a selective filter could return far fewer rows than
+  requested. Filters now apply *before* the search: `limit k` means the
+  top-k of *matching* rows. Filtered search results will change — they are
+  now correct.
+
+- **Undirected edge traversal.** `$a <edgeName> $b` matches an edge in either
+  direction with set semantics (a pair connected both ways appears once), for
+  same-endpoint-type edges (e.g. `Related: Issue -> Issue`); asymmetric edges
+  are rejected at typecheck (T22). Composes with hop bounds
+  (`$a <knows>{1,3} $b`) and `not { }` ("no edge in either direction"). One
+  pattern replaces the query-both-directions-and-merge workaround.
+
+- **Enum widening in schema migration.** Adding variants to an `enum(...)`
+  property is now a supported, metadata-only migration step — `schema plan`
+  shows `extend enum`, `apply` touches no table data, and the new variants
+  are accepted immediately on every write surface. Narrowing, variant
+  renames, and enum↔String conversions still refuse (OG-MF-106).
+
+- **Embedding validation hardened.** Non-finite embeddings (NaN/Inf) and
+  zero vectors are rejected at the client boundary instead of being stored;
+  the JSONL loader rejects non-numeric vector elements (previously coerced
+  to 0.0); and forcing the mock embedding provider over an explicitly
+  configured real one now logs a warning.
+
+- **Blob-bearing tables rejoin maintenance.** With Lance 9's blob-column
+  compaction support, `optimize` now includes tables with `Blob` properties
+  — fragment reclamation and index folding cover them like any other table.
+
+- **Self-service upgrade refusals.** Opening a graph from an older storage
+  format now names the release line that wrote it (e.g. "created by omnigraph
+  0.6.2 to 0.7.2") and the exact export → init → load commands, instead of
+  asking the operator to identify the right binary themselves.
+
+## Behavior changes
+
+- Filtered `nearest()`/`bm25()` result sets change (see above) — previously
+  missing results now appear.
+- New inverted indexes are written in Lance's FTS v2 format (readable by
+  omnigraph ≥ 0.8.0 binaries), and text-search `AND` semantics were refined
+  upstream, so `match_text`/`bm25` rankings may shift slightly.
+- Loads that previously succeeded with non-numeric vector elements or
+  non-finite embeddings now fail loudly at write time.
+
+## Upgrade notes
+
+- **No storage-format change.** v0.8.0 graphs open unchanged; downgrade to
+  v0.8.0 remains possible (same internal schema v4).
+- Upgrading the binary is the complete fix for the two substrate issues
+  above — no data repair, no rebuild.
+- The substrate is a rev-pinned Lance pre-release (9.0.0-beta.15), adopted
+  ahead of the stable release to deliver the fixes above promptly. v0.9.0
+  moves to Lance 9.0.0 stable.
+
+## Developer-facing
+
+- Scenario benchmark harness (`cargo bench -p omnigraph-engine --bench
+  scenarios`): cold subprocess runs measuring wall-clock + peak RSS, JSON-line
+  results with a persistent log — a decision instrument, never a CI gate.
+- A gated cross-version upgrade test (`OMNIGRAPH_OLD_BIN`) proves a genuine
+  v3-format graph is refused with the release-named message and rebuilds via
+  the documented path; run on demand, not in CI.
+- One dataset-open chokepoint (`instrumentation::open_dataset`) with the
+  shared per-graph Lance `Session` attached to write-side opens — the local
+  merge-scan cost term is now flat in commit history.