fix(ci): notify-chart-dev gate avoids SIGPIPE; add workflow_dispatch

The gate step's `git tag --points-at HEAD | grep -q '^zddc-server-v'`
exits 141 (SIGPIPE) under bash's pipefail when grep finishes early —
the runner's strict-mode wrapper then fails the step even though the
if-condition logic completed correctly. Materialize the tag list with
git's native --list glob filter and test it with `[ -n ]` instead, so
no pipeline is involved.

Also add workflow_dispatch so we can re-fire this workflow on a fresh
commit without needing a no-op edit under zddc/internal/apps/embedded/
to match the paths filter.

.forgejo/workflows/notify-chart-dev.yml

@@ -18,6 +18,10 @@ on:
     branches: [main]
     paths:
       - 'zddc/internal/apps/embedded/**'
+  # Manual trigger — useful for re-firing after a workflow fix without
+  # also having to make a no-op embedded/ change to satisfy the paths
+  # filter. Run on the latest main commit; gate-step still applies.
+  workflow_dispatch:
 
 jobs:
   notify-chart-dev:
@@ -39,9 +43,15 @@ jobs:
         id: gate
         run: |
           set -eu
-          if git tag --points-at HEAD | grep -q '^zddc-server-v'; then
+          # Avoid `git tag | grep -q ^zddc-server-v` — under bash's
+          # default `pipefail`, grep -q closing stdin early gives git
+          # SIGPIPE (exit 141), which the runner's strict-mode wrapper
+          # treats as a step failure even though the if-condition logic
+          # is correct. Materialize the tag list first, then test it.
+          STABLE_TAGS=$(git tag --points-at HEAD --list 'zddc-server-v*')
+          if [ -n "$STABLE_TAGS" ]; then
               echo "is_beta=false" >> "$GITHUB_OUTPUT"
-              echo "HEAD has zddc-server-v* tag — stable workflow handles this; skipping dev notify"
+              echo "HEAD has zddc-server-v* tag ($STABLE_TAGS) — stable workflow handles this; skipping dev notify"
           else
               echo "is_beta=true" >> "$GITHUB_OUTPUT"
               echo "No stable tag at HEAD; treating as beta cut"