feat: add plugin name prefixes to hooks and improve git-flow sync

- Add [plugin-name] prefix to all hook messages for better identification
- Make doc-guardian hook notification-only (non-blocking)
- Add stale branch detection to /commit-sync with git fetch --prune
- Enhance /branch-cleanup to handle stale branches separately

Closes improvements for hook UX and git workflow

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plugins/git-flow/commands/commit-sync.md

@@ -2,7 +2,7 @@
 
 ## Purpose
 
-Full sync operation: commit local changes, push to remote, and sync with upstream/base branch.
+Full sync operation: commit local changes, push to remote, sync with upstream/base branch, and clean up stale remote-tracking branches.
 
 ## Behavior
 
@@ -19,8 +19,8 @@ Push committed changes to remote branch.
 Pull latest from base branch and rebase/merge:
 
 ```bash
-# Fetch all
-git fetch --all
+# Fetch all with prune (removes stale remote-tracking refs)
+git fetch --all --prune
 
 # Rebase on base branch
 git rebase origin/<base-branch>
@@ -29,7 +29,26 @@ git rebase origin/<base-branch>
 git push --force-with-lease
 ```
 
-### Step 4: Report Status
+### Step 4: Detect Stale Local Branches
+
+Check for local branches tracking deleted remotes:
+
+```bash
+# Find local branches with gone upstreams
+git branch -vv | grep ': gone]'
+```
+
+If stale branches found, report them:
+
+```
+Stale local branches (remote deleted):
+  - feat/old-feature (was tracking origin/feat/old-feature)
+  - fix/merged-bugfix (was tracking origin/fix/merged-bugfix)
+
+Run /branch-cleanup to remove these branches.
+```
+
+### Step 5: Report Status
 
 ```
 Sync complete:
@@ -40,6 +59,10 @@ Base:   development @ xyz7890 (synced)
 
 Your branch is up-to-date with development.
 No conflicts detected.
+
+Cleanup:
+  Remote refs pruned: 2
+  Stale local branches: 2 (run /branch-cleanup to remove)
 ```
 
 ## Environment Variables
@@ -48,6 +71,7 @@ No conflicts detected.
 |----------|---------|-------------|
 | `GIT_DEFAULT_BASE` | `development` | Branch to sync with |
 | `GIT_SYNC_STRATEGY` | `rebase` | How to incorporate upstream changes |
+| `GIT_AUTO_PRUNE` | `true` | Auto-prune stale remote refs on sync |
 
 ## Conflict Handling
 
@@ -76,4 +100,5 @@ Pushed to: origin/feat/password-reset
 Synced with: development (xyz7890)
 
 Status: Clean, up-to-date
+Stale branches: None (or N found - run /branch-cleanup)
 ```