ci: 20-minute job timeouts

A hung apt mirror on the runner otherwise holds a job until the
6-hour default limit; every job normally finishes in minutes.

.github/workflows/ci.yml

@@ -8,6 +8,7 @@ on:
 jobs:
   check-and-test:
     runs-on: ubuntu-latest
+    timeout-minutes: 20
     steps:
       - uses: actions/checkout@v4
       # CLAUDE.md is read at every session start; detail belongs in the nested files.
@@ -29,6 +30,7 @@ jobs:
   # The re-save-through-LibreOffice leg, which self-skips everywhere soffice is absent.
   lo-roundtrip:
     runs-on: ubuntu-latest
+    timeout-minutes: 20
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
@@ -43,6 +45,7 @@ jobs:
   # regressions the jsdom suite cannot see.
   smoke:
     runs-on: ubuntu-latest
+    timeout-minutes: 20
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4