fix(optimize): skip blob-bearing tables to avoid Lance compaction crash (#138)

* test(optimize): pin Lance blob-column compaction failure as a surface guard

Lance compact_files mis-decodes blob-v2 columns under its forced BlobHandling::AllBinary read ("more fields in the schema than provided column indices"), failing even a pristine uniform-V2_2 multi-fragment blob table; reads use descriptor handling and are unaffected.

Guard 10 reproduces this and is self-retiring: it turns red on the Lance bump that fixes the bug, forcing LANCE_SUPPORTS_BLOB_COMPACTION to flip.

* fix(optimize): skip blob-bearing tables instead of crashing compaction

omnigraph optimize aborted the whole sweep when any node/edge table had a Blob property: Lance compact_files cannot decode blob-v2 columns under AllBinary (the column-index error pinned by the surface guard). Skip blob-bearing tables behind a LANCE_SUPPORTS_BLOB_COMPACTION gate and report them via TableOptimizeStats.skipped / SkipReason (surfaced in the CLI and a tracing::warn) instead of erroring, which also isolates the failure so the other tables still compact.

Reads/writes are unaffected; only fragment/space reclamation on blob tables is deferred until the upstream Lance fix. Adds a maintenance.rs regression test (validated red with the column-index symptom before the fix, green after), a concise v0.6.1 release note, and updates docs (maintenance, cli-reference, AGENTS capability matrix, invariants Known Gaps, lance.md audit, constants).

* refactor(optimize): make TableOptimizeStats and SkipReason non_exhaustive

Both are returned result types, never built by callers, so #[non_exhaustive] makes this the last field/variant addition that can break downstream literal construction and keeps future ones non-breaking (review feedback on the public-field addition). The v0.6.1 Compatibility Notes call out the source-level change.

Also drops the now-stale "RED today / GREEN after the fix lands" narration in the optimize_skips_blob_table_and_reports_skip test (historical regression context now that the fix is in this branch), and folds in the expanded v0.6.1 release note.

* chore(release): bump workspace to v0.6.1

Coherent version bump to accompany the v0.6.1 release note: all five crate manifests + path-dependency constraints, Cargo.lock, the AGENTS.md surveyed-version line, and openapi.json info.version move 0.6.0 -> 0.6.1. Matches the established release pattern (#118 landed the v0.6.0 note + bump together) and resolves the Codex/Devin review flag that a v0.6.1 note without a bump leaves CARGO_PKG_VERSION reporting 0.6.0 and mixed package versions.

docs/user/cli-reference.md

@@ -21,7 +21,7 @@ A reference for the `omnigraph` binary's command surface and `omnigraph.yaml` sc
 | `schema plan \| apply \| show (alias: get)` | migrations |
 | `lint` (alias: `check`) | offline / graph-backed query validation. Replaces `query lint` / `query check`, which are kept as deprecated argv-level shims that print a one-line warning and rewrite to `omnigraph lint` |
 | `queries validate \| list` | operate on the server-side stored-query registry (the `queries:` block). `validate` type-checks every stored query against the live schema offline (opens the selected graph; exits non-zero on any breakage), catching schema drift without restarting the server; `list` prints the selected registry's query names, MCP exposure, and typed params. For per-graph registries, pass `--target <graph>` or set `cli.graph`; with no graph selection, `list` shows only top-level `queries:`. Distinct from `lint`, which validates a single `.gq` file |
-| `optimize` | non-destructive Lance compaction |
+| `optimize` | non-destructive Lance compaction (skips tables with `Blob` columns; `--json` reports a `skipped` field) |
 | `cleanup --keep N --older-than 7d --confirm` | destructive version GC |
 | `embed` | offline JSONL embedding pipeline |
 | `policy validate \| test \| explain` | Cedar tooling. Selects `cli.graph`, else `server.graph`, else top-level `policy.file` |