fix: limit dagger-data volume growth by pruning named caches (#193)

The plain `prune` operation only removes unreferenced execution-cache
entries; named cache volumes (gradle-cache, go-build-cache, go-mod-cache,
pip-cache) are never reclaimed and grow without bound, causing the
dagger-data Docker volume to reach 200 GB over time.

Pass maxUsedSpace/targetSpace arguments to `prune` so Dagger also
reclaims named volumes when the total cache exceeds 75 GB, targeting
50 GB. Use an aggressive targetSpace of 20 GB for disk-space emergency
recovery in check-dagger. Add a dagger-prune task for manual use.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.forgejo/workflows/ci.yml

@@ -55,7 +55,10 @@ jobs:
       - name: Prune Dagger cache before check
         env:
           DAGGER_NO_NAG: "1"
-        run: dagger query '{ engine { localCache { prune } } }' 2>/dev/null || true
+        # prune(maxUsedSpace) also reclaims named cache volumes (gradle-cache, go-build-cache, etc.)
+        # when total cache exceeds the limit; without args only unreferenced entries are removed.
+        run: |
+          dagger query '{ engine { localCache { prune(maxUsedSpace: "75gb", targetSpace: "50gb") } } }' || true
 
       - name: Run Full Check Suite
         env:
@@ -66,7 +69,8 @@ jobs:
         if: always()
         env:
           DAGGER_NO_NAG: "1"
-        run: dagger query '{ engine { localCache { prune } } }' 2>/dev/null || true
+        run: |
+          dagger query '{ engine { localCache { prune(maxUsedSpace: "75gb", targetSpace: "50gb") } } }' || true
 
       - name: Cleanup TLS credentials
         if: always()

Taskfile.yml

@@ -288,7 +288,7 @@ tasks:
               echo "$(_ts) dagger: network error on attempt $attempt/3, retrying..." >&2
             elif [ "$attempt" -lt 3 ] && grep -q "No space left on device" "$DAGGER_OUT"; then
               echo "$(_ts) dagger: disk space error on attempt $attempt/3, pruning Dagger cache..." >&2
-              dagger query '{ engine { localCache { prune } } }' 2>/dev/null || true
+              dagger query '{ engine { localCache { prune(targetSpace: "20gb") } } }' 2>/dev/null || true
               echo "$(_ts) dagger: waiting 90s for freed space to settle..." >&2
               sleep 90
             else
@@ -320,6 +320,12 @@ tasks:
         wait "$RECV_PID" 2>/dev/null || true
         exit $RC
 
+  dagger-prune:
+    desc: Prune the Dagger engine cache (keeps named volumes unless total exceeds 75 GB, then targets 50 GB)
+    cmds:
+      - |
+        dagger query '{ engine { localCache { prune(maxUsedSpace: "75gb", targetSpace: "50gb") } } }'
+
   integration-android:
     desc: UI integration tests on a connected Android emulator (Stalwart on host, emulator reaches it via 10.0.2.2)
     deps: [_preflight, _android-sdk-check, _android-avd-setup]