ci: skip test matrix on docs-only changes + add job timeouts

- paths-ignore '**/*.md' on push/pull_request so a CHANGELOG/README-only PR
  doesn't spin up the (self-hosted, sometimes-offline) Windows test job.
- timeout-minutes on lint (10) / test (15) / catalog-signature (10) so a job
  that hangs mid-run fails instead of hanging forever.

Note: timeout-minutes counts from job start, so it does not rescue a job stuck
'Waiting to run' when the Windows runner is offline — paths-ignore covers the
docs case; code PRs still need the runner up.

.github/workflows/ci.yml

@@ -3,13 +3,16 @@ name: CI
 on:
   push:
     branches: [main]
+    paths-ignore: ["**/*.md"]
   pull_request:
+    paths-ignore: ["**/*.md"]
   workflow_dispatch:
 
 jobs:
   lint:
     runs-on: ubuntu-latest
     name: Lint (ruff)
+    timeout-minutes: 10
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -31,6 +34,11 @@ jobs:
   test:
     runs-on: ${{ matrix.os }}
     name: Tests (py${{ matrix.python }} / ${{ matrix.os }})
+    # Guards against a job that hangs mid-run (e.g. a wedged test). Note: this
+    # counts from when a runner PICKS UP the job, so it does not rescue a job
+    # stuck "Waiting to run" because the self-hosted Windows runner is offline —
+    # for that, bring the runner back or skip via paths-ignore (docs).
+    timeout-minutes: 15
     strategy:
       fail-fast: false
       matrix:
@@ -85,6 +93,7 @@ jobs:
   catalog-signature:
     name: Catalog signature
     runs-on: ubuntu-latest
+    timeout-minutes: 10
     steps:
       - uses: actions/checkout@v4