docs(designs): drop paths: filter from semver-gate workflow

Per review on PR #9057: a workflow that uses on.pull_request.paths:
to fire only on relevant changes cannot also be a required branch-
protection check. When paths don't match, the workflow doesn't run,
no status posts, and branch protection treats the required check as
missing/pending — blocking the PR.

check_semver_bump.py already self-gates (returns exit 0 when no
expected.*.yaml files changed), so dropping the paths filter and
running unconditionally is the canonical fix for the "skipped but
required check" pitfall. The script does the gating; the workflow
just runs it.

Author: bnusunny

designs/golden_templates_and_semver_check.md

@@ -254,18 +254,25 @@ can never diverge.
 ### The semver gate
 
 Tiny standalone GitHub workflow at
-`.github/workflows/golden-semver-gate.yml`. Fires only when corpus pins or
-the version file change:
+`.github/workflows/golden-semver-gate.yml`. Runs on every PR; the script
+itself returns exit 0 when no corpus pins changed, so it's cheap to run
+unconditionally and posts a definitive status on every PR (which lets
+branch protection mark it as a required check without blocking
+unrelated PRs):
 
 ```yaml
 on:
   pull_request:
     branches: [develop, "feat/*", "feat-*"]
-    paths:
-      - "tests/golden/templates/**/expected.*.yaml"
-      - "samcli/__init__.py"
 ```
 
+The workflow does *not* use `on.pull_request.paths:` filtering. Path
+filtering at the trigger level skips the workflow entirely on PRs that
+touch no matching path — no status posts, and a required check that
+never reports gets treated by branch protection as missing/pending.
+Self-gating in the script (return 0 when there are no relevant changes)
+is the simpler fix and keeps the check eligible to be required.
+
 `check_semver_bump.py` rules:
 
 1. Diff merge base vs HEAD; collect changes to