fix(ci): prune Dagger cache on disk-space error and before check

Previous fix (retry × 3 with 60 s sleep) was not enough: all three
attempts still failed because the engine cache stayed full throughout.
Add an explicit `dagger query '{ engine { localCache { prune } } }'`
call (a) as a proactive step in ci.yml right after the stunnel setup,
and (b) inside the retry handler before each back-off sleep (now 90 s
instead of 60 s). The prune evicts stale execution-cache snapshots
(e.g. old pubspec.lock layers) so fresh disk is available when flutter
pub get runs. The `|| true` guard makes the prune non-fatal if the
query syntax changes between Dagger versions.

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

.forgejo/workflows/ci.yml

@@ -30,6 +30,11 @@ jobs:
           DAGGER_CLIENT_KEY: ${{ secrets.DAGGER_CLIENT_KEY }}
         run: scripts/setup_dagger_remote.sh
 
+      - name: Prune Dagger cache before check
+        env:
+          DAGGER_NO_NAG: "1"
+        run: dagger query '{ engine { localCache { prune } } }' 2>/dev/null || true
+
       - name: Run Full Check Suite
         env:
           DAGGER_NO_NAG: "1"

Taskfile.yml

@@ -287,8 +287,10 @@ tasks:
             if [ "$attempt" -lt 3 ] && grep -qE "connection reset|context canceled|connection refused" "$DAGGER_OUT"; then
               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 $attempt/3, waiting 60s for space to free up..." >&2
-              sleep 60
+              echo "$(_ts) dagger: disk space error on attempt $attempt/3, pruning Dagger cache..." >&2
+              dagger query '{ engine { localCache { prune } } }' 2>/dev/null || true
+              echo "$(_ts) dagger: waiting 90s for freed space to settle..." >&2
+              sleep 90
             else
               return "$RC"
             fi