docs: document V1a config/CLI (version/storage/servers/--graph); mark RFC landed

Sweep `--target` → `--graph` across the user docs (cli-reference, cli, server,
policy) and update `omnigraph.example.yaml` to the v1 schema (`version: 1`,
`storage:`, `servers:`/`server:`). Add the typed-locator schema (version/storage/
servers/graph_id + strictness) to cli-reference, and a server "embedded graphs
only" note. The RFC gets an Implementation-status banner recording V1a as landed
and its divergences (`--target` removed outright — no alias; `uri:` deprecation-
warned) and corrects the stale `QueryRegistry`/config-location claims (it's in
`omnigraph-queries` / `omnigraph-config` now). testing.md gains a Config & CLI
note. Past release notes keep `--target` (accurate for those versions);
`--target-branch` untouched.

omnigraph.example.yaml

@@ -1,8 +1,14 @@
+version: 1
+
+servers:
+  prod:
+    endpoint: http://127.0.0.1:8080
+
 graphs:
   local:
-    uri: ./repo.omni
+    storage: ./repo.omni
   dev:
-    uri: http://127.0.0.1:8080
+    server: prod
     bearer_token_env: OMNIGRAPH_BEARER_TOKEN
 
 cli: