ci: skip the gate for docs-only changes

Add paths-ignore (docs/**, **/*.md) to the gate's push + pull_request
triggers so markdown/docs-only changes don't run a full clippy+test that
can't change the outcome. Mixed code+docs pushes still gate (not all
files are ignored); flake/toolchain changes are deliberately not ignored.
Also refresh a stale ADR-0049 -> ADR-ci-002 comment reference.

.gitea/workflows/ci.yaml

@@ -2,7 +2,7 @@
 # build-ci-image.yaml), so the pinned 1.95.0 toolchain is already warm — steps
 # just enter the flake devShell and run cargo.
 #
-# Gate = clippy + test. fmt is deliberately NOT gated yet (ADR-0049: the tree
+# Gate = clippy + test. fmt is deliberately NOT gated yet (ADR-ci-002: the tree
 # isn't clean under stock rustfmt; revisit on main). The release job (static
 # binary for D2) and the platform matrix layer on later, step by step.
 name: ci
@@ -13,7 +13,17 @@ on:
     # run (the release workflow owns tags). Pushing commits + a tag together
     # still gates the commits via the branch push.
     branches: ['**']
+    # Skip the gate for docs-only changes — markdown can't affect clippy/test.
+    # A push touching code *and* docs still runs (not all files are ignored).
+    # Note: flake/toolchain changes are NOT ignored — they can shift the
+    # toolchain and thus lint/test outcomes.
+    paths-ignore:
+      - 'docs/**'
+      - '**/*.md'
   pull_request:
+    paths-ignore:
+      - 'docs/**'
+      - '**/*.md'
 
 jobs:
   gate: