housekeeping.yml (daily sweep, #83) and its test in ci.yml

The sweep itself landed in #115; the workflow is the owner's merge. Dry-run unless TIME_MODE=live (which the repo sets).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017K4vyY3yUD3GsvoZaAtKkD

.github/workflows/ci.yml

@@ -19,3 +19,4 @@ jobs:
           node-version: 22
       - run: python3 .github/time/test_time.py
       - run: python3 .github/time/test_seed.py
+      - run: python3 .github/time/test_housekeeping.py

.github/workflows/housekeeping.yml

@@ -0,0 +1,26 @@
+name: housekeeping
+# The daily sweep (#83, .github/time/housekeeping.py): prunes merged branches, closes spent signal issues and empty
+# milestones, lists the stale on the Astra log. Deterministic, no model calls; dry-run unless TIME_MODE=live.
+# SOP: .agents/skills/housekeeping/SKILL.md
+on:
+  schedule:
+    - cron: "17 13 * * *"   # a few minutes after the Astra tick (13:13)
+  workflow_dispatch:
+concurrency:
+  group: housekeeping
+  cancel-in-progress: false
+jobs:
+  sweep:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v5
+        with:
+          sparse-checkout: .github/time
+          persist-credentials: false
+      - run: python3 .github/time/housekeeping.py
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          TIME_TOKEN: ${{ secrets.TIME_TOKEN }}   # branch and issue writes go out as the `time` user
+          TIME_MODE: ${{ vars.TIME_MODE }}
+          TIME_VENTURE_MEASURE_DAYS: ${{ vars.TIME_VENTURE_MEASURE_DAYS }}