Teach draft-release-notes classifier that metadata.yaml is documentation only

Author: trask

.github/scripts/draft-release-notes/rules.md

@@ -92,6 +92,26 @@ behavior is a bug fix, not an enhancement — diffs that remove an
 over-restrictive condition, add a fallback branch, or invert an `&&`
 usually belong here. Describe the user-visible symptom.
 
+## metadata.yaml is documentation, not evidence
+
+Files named `metadata.yaml` (typically under
+`instrumentation/<name>/metadata.yaml`) are static documentation
+describing each module's configs, libraries, and semconv surfaces.
+They are read by tooling (instrumentation-list generation, declarative-
+config bridge) but not by runtime instrumentation.
+
+Adding, renaming, or filling in entries in `metadata.yaml` does NOT
+introduce, rename, or change any user-facing config. The corresponding
+config property already exists in `src/main` Java code, and its name is
+unaffected by the YAML diff. A `declarative_name:` value added to a
+`metadata.yaml` entry is the declarative-config alias for an existing
+flat property; it is not a new mapping or a runtime change.
+
+When the only `src/main` evidence is a metadata.yaml entry — even one
+that names a real-looking config property — set `decision: "omit"` with
+a surface like "metadata.yaml documentation only". Do not emit an
+Enhancements bullet that introduces a config the diff merely documents.
+
 ## When to omit
 
 Omit only when the PR's `src/main` runtime changes are entirely limited
@@ -101,7 +121,8 @@ to one or more of:
 - test-only changes, cross-testing, moving tests out of default packages,
 - CI/build-tooling with no runtime effect,
 - renames of internal (not extension-API) fields, packages, or helpers,
-- new package-private, `internal`-package, or test-only methods.
+- new package-private, `internal`-package, or test-only methods,
+- `metadata.yaml` documentation (see section above).
 
 Trivial omits (renovate bumps, all-test/docs/build paths, post-release
 version bumps) are handled by `classify.py --preclassify-only`.