ci: stop double-running lint + skill-docs on every PR commit

Both fired on unrestricted push AND pull_request, so each PR push ran
them twice (12 duplicate (headSha, workflow) pairs in the last 200 runs).
push is now main-only; pull_request covers PR branches.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/actionlint.yml

@@ -1,5 +1,10 @@
 name: Workflow Lint
-on: [push, pull_request]
+# push is main-only: a push to a PR branch already fires the pull_request run;
+# the unrestricted push trigger double-ran every PR commit.
+on:
+  push:
+    branches: [main]
+  pull_request:
 
 # Cancel superseded runs for the same branch (matches evals.yml,
 # windows-free-tests.yml, etc.). head_ref is set on pull_request; ref_name is

.github/workflows/skill-docs.yml

@@ -1,5 +1,10 @@
 name: Skill Docs Freshness
-on: [push, pull_request]
+# push is main-only: a push to a PR branch already fires the pull_request run;
+# the unrestricted push trigger double-ran every PR commit.
+on:
+  push:
+    branches: [main]
+  pull_request:
 
 # Cancel superseded runs for the same branch (matches evals.yml,
 # windows-free-tests.yml, etc.). head_ref is set on pull_request; ref_name is