docs(skill): align the omnigraph skill with 0.8.1

skills/omnigraph/SKILL.md

@@ -2,10 +2,10 @@
 name: omnigraph
 description: Store, retrieve, and query knowledge, memory, and relationships in an Omnigraph graph, and operate a local or remote Omnigraph deployment. Use when the user wants to capture or recall facts, notes, or entities, build or query a knowledge graph or agent memory, or run Omnigraph — and whenever you see Omnigraph CLI commands (omnigraph init/query/mutate/load/schema/lint/embed/branch/commit/login/profile/cluster), .pg schema or .gq query files, s3:// graph URIs, bearer-authed graph endpoints, 504 errors, or a cluster.yaml / omnigraph.yaml / ~/.omnigraph/config.yaml. Covers cluster-mode deployments (cluster.yaml plan/apply, omnigraph-server --cluster), the two config surfaces (cluster.yaml + ~/.omnigraph/config.yaml), schema evolution, query linting, data writes (mutate; load needs --mode/--from), branches, embeddings, Cedar policy, and remote ops. Especially important before schema apply (plan first), any load (--mode required), any .gq/.pg edit (lint after), or any remote write (verify via commit list).
 license: MIT (see LICENSE at repo root)
-compatibility: Requires omnigraph CLI >= 0.7.0 — the unified `load`, the two config surfaces (cluster.yaml + ~/.omnigraph/config.yaml), and cluster apply/serve all require 0.7.0.
+compatibility: Requires omnigraph CLI >= 0.7.0 — the unified `load`, the two config surfaces (cluster.yaml + ~/.omnigraph/config.yaml), and cluster apply/serve all require 0.7.0. Version-gated features are marked inline (undirected traversal `<edge>` and enum widening in `schema apply` require >= 0.8.1).
 metadata:
   author: ModernRelay
-  version: "0.7.0"
+  version: "0.8.1"
   repository: https://github.com/ModernRelay/omnigraph
 ---
 
@@ -96,7 +96,8 @@ The non-obvious facts that bite, then the full grammar:
 - **Scalar param types**: `String Bool I32 I64 U32 U64 F32 F64 DateTime Date Blob`. Modifiers: `T?` (optional), `[T]` (list), `Vector(N)`. There is **no `Int`** — use `I64`.
 - **A read query needs `match` *and* `return`** (`order`/`limit` optional); a mutation has neither — only `insert`/`update`/`delete`.
 - **`limit` takes an integer literal, not a param** — `limit 50`, never `limit $n`.
-- **Variable-hop traversal**: `$p knows{1,3} $f` (`{1,}` = unbounded).
+- **Variable-hop traversal**: `$p knows{1,3} $f` — bounds are **required to be finite** (`{1,}` is rejected: "unbounded traversal is disabled").
+- **Undirected traversal** (omnigraph >= 0.8.1): `$p <knows> $f` matches the edge in either direction, deduplicated (a pair connected both ways appears once). Same-endpoint-type edges only (e.g. `Related: Issue -> Issue`) — asymmetric edges are rejected (T22). Composes with bounds (`$p <knows>{1,3} $f`) and `not { }`. Replaces the query-both-directions-and-merge workaround for symmetric relations.
 - **Literals & calls**: `now()`, `date("2026-04-29")`, `datetime("…T00:00:00Z")`, list `[…]`.
 - **Filters** `= != > < >= <= contains`; **aggregates** `count/sum/avg/min/max` (`count($f) as n`).
 - **Stored-query metadata**: `@description("…")` / `@instruction("…")` may follow the param list.
@@ -159,8 +160,9 @@ prop_match_list = { prop_match ~ ("," ~ prop_match)* ~ ","? }
 prop_match = { ident ~ ":" ~ match_value }
 match_value = { literal | variable | now_call }
 
-// Traversal: $p knows $f
-traversal = { variable ~ edge_ident ~ traversal_bounds? ~ variable }
+// Traversal: $p knows $f (directional) or $p <knows> $f (undirected, >= 0.8.1)
+traversal = { variable ~ (undirected_edge | edge_ident) ~ traversal_bounds? ~ variable }
+undirected_edge = { "<" ~ edge_ident ~ ">" }
 traversal_bounds = { "{" ~ integer ~ "," ~ integer? ~ "}" }
 
 // Filter: $f.age > 25
@@ -375,7 +377,7 @@ These are the traps most likely to bite. Scan this table before debugging any pa
 | `load --mode merge` after `@embed` source change | stale embeddings | `omnigraph embed --reembed_all` or `load --mode overwrite` |
 | `schema apply` with feature branches open | rejected | Merge or delete branches first |
 | `nearest(...)` / `bm25(...)` / `rrf(...)` without `limit` | compile error | Add `limit N` |
-| Adding non-nullable property without backfill | unsupported migration | Make optional → backfill → tighten in follow-up apply |
+| Adding non-nullable property without backfill | unsupported migration | Make optional → backfill; keep it optional (tightening `T?` → `T` is refused, OG-MF-106) |
 | `omnigraph init --json` | `unexpected argument --json` | `init` doesn't support `--json`; drop the flag |
 | `omnigraph init` on an already-initialized URI | `AlreadyInitialized` error (v0.6.0+) | `--force` to re-init (skips the schema preflight; does **not** purge data) |
 | `schema apply` dropping a property/type | soft-dropped or rejected (no data loss) | add `--allow-data-loss` to actually drop the column |

skills/omnigraph/references/queries.md

@@ -115,6 +115,26 @@ query employees_of($company: String) {
 }
 ```
 
+### Undirected traversal (omnigraph >= 0.8.1)
+
+For symmetric relations (same-endpoint-type edges like `IssueRelated: Issue -> Issue`),
+angle brackets match the edge in **either direction**, deduplicated — one
+pattern replaces querying both directions and merging:
+
+```gq
+query related_to($slug: String) {
+    match {
+        $i: Issue { slug: $slug }
+        $i <issueRelated> $r
+    }
+    return { $r.slug }
+}
+```
+
+Composes with hop bounds (`$a <knows>{1,3} $b`) and `not { }` ("no edge in
+either direction"). Asymmetric edges (e.g. `Comment -> Issue`) are rejected at
+typecheck (T22) — use the directional form there.
+
 ### Negation
 
 ```gq
@@ -271,7 +291,7 @@ query add_and_link($slug: String, $pattern: String, $createdAt: DateTime, $updat
 
 There's no `upsert` keyword at the query level — use `load --mode merge` for bulk upsert.
 
-> **Insert/update-only OR delete-only (the D₂ rule).** A single mutation query may contain inserts and updates, **or** deletes — never both. Mixing a `delete` with an `insert`/`update` in the same query is rejected at parse time. (Inserts/updates go through a staged two-phase publish; deletes inline-commit — omnigraph doesn't yet use Lance's two-phase delete API (it shipped in Lance 7.0.0 but isn't wired in) — so they can't share one atomic statement.) Split a delete-then-insert into two separate mutations.
+> **Insert/update-only OR delete-only (the D₂ rule).** A single mutation query may contain inserts and updates, **or** deletes — never both. Mixing a `delete` with an `insert`/`update` in the same query is rejected at parse time. (Deletes stage through the same two-phase publish as inserts/updates since 0.8.0; the D₂ split is a deliberate semantic boundary — one mutation query is constructive XOR destructive, keeping read-your-writes unambiguous — not an implementation gap.) Split a delete-then-insert into two separate mutations.
 
 ### Date and DateTime values
 

skills/omnigraph/references/schema.md

@@ -106,7 +106,17 @@ Adding a non-nullable property to an existing node is rejected as unsupported. P
 1. Add as optional: `new_prop: String?`
 2. Apply
 3. Backfill via a `mutate` or `load --mode merge`
-4. Tighten to required in a follow-up apply: `new_prop: String`
+4. Keep it optional: tightening `T?` -> `T` is currently refused by the planner
+   (a property-type change, OG-MF-106). Enforce presence at write time by
+   convention until required-tightening ships as a migration step.
+
+### Enum widening is a supported apply (omnigraph >= 0.8.1)
+
+Adding variants to an `enum(...)` property is a metadata-only migration step:
+`schema plan` shows `extend enum ...`, `apply` touches no table data, and new
+variants are accepted immediately on every write surface. Narrowing, renaming
+a variant, or converting enum <-> `String` still refuse (OG-MF-106) — those
+remain rebuild territory. Value *order* never matters (values are normalized).
 
 ### Keep `@key` stable