chore(docs): move openapi spec to resources for split prep

Moves the canonical OpenAPI 3.1 spec from docs/openapi.yaml to
resources/openapi.yaml so it ships inside the daemon JAR and can be
served via io/resource. After the upcoming repo split, docs/ is
removed from this repo entirely; the website (in noumenon-site) will
mirror this file from raw.githubusercontent.com on a cron schedule.

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

Author: leifericf

README.md

@@ -156,7 +156,7 @@ noum <command> [options]    # single-shot mode
 noum help <command>         # command-specific help
 ```
 
-Run `noum help` for the full command list. The CLI and MCP server expose the same capabilities. See [`docs/openapi.yaml`](docs/openapi.yaml) for the HTTP API spec.
+Run `noum help` for the full command list. The CLI and MCP server expose the same capabilities. See [`resources/openapi.yaml`](resources/openapi.yaml) for the HTTP API spec.
 
 ## Development