feat: Auto-reset /sync to master when nothing blocks

Previously /sync only reported state and suggested manual commands.
Now it automatically runs git checkout master && git pull --rebase
when the working tree is clean, the branch has no unpushed commits,
and we're not already on master. If blockers exist (dirty files,
unpushed commits), it reports them and asks what to do instead.

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

Author: stranma

.claude/skills/sync/SKILL.md

@@ -18,13 +18,20 @@ Pre-flight workspace sync. Run this before starting any work.
    - Run `git status` to see dirty files, staged changes, untracked files
    - Run `git branch -vv` to see current branch, tracking info, ahead/behind counts
 
-3. **Warn on problems**
-   - If behind remote: warn and suggest `git pull --rebase` or `git rebase origin/<branch>`
-   - If on main/master with dirty working tree: warn that uncommitted changes exist on the base branch
-   - If no upstream tracking branch: note that the branch is local-only
+3. **Auto-reset to master if nothing is blocking**
+
+   If ALL of the following are true, automatically run `git checkout master && git pull --rebase` without asking:
+   - Working tree is clean (no staged, unstaged, or untracked changes that matter)
+   - Current branch is NOT master (already on a feature branch that can be left)
+   - The feature branch has no unpushed commits (ahead 0, or branch was already merged)
+
+   If any blocker exists, do NOT auto-reset. Instead report the blocker and ask what to do:
+   - **Dirty working tree**: list the files and ask whether to stash, commit, or discard
+   - **Unpushed commits on current branch**: warn and ask whether to push first or switch anyway
+   - **Already on master**: just `git pull --rebase` to update
 
 4. **Show recent context**
-   - Run `git log --oneline -3` to show the last 3 commits
+   - Run `git log --oneline -3` to show the last 3 commits (after any branch switch)
 
 5. **Output structured report**
 
@@ -35,19 +42,14 @@ Branch: <name> (tracking: <remote>/<branch>)
 Status: <clean | N dirty files | N staged, M unstaged>
 Remote: <up to date | N ahead, M behind>
 
-## Warnings
-- <any warnings from step 3, or "None">
+## Actions Taken
+- <e.g. "Switched to master and pulled 5 new commits", or "None -- already on clean master">
+
+## Blockers (if any)
+- <e.g. "Unstaged changes in .claude/settings.json -- stash, commit, or discard?">
 
 ## Recent Commits
 - <hash> <message>
 - <hash> <message>
 - <hash> <message>
 ```
-
-## What This Skill Does NOT Do
-
-- Does NOT classify the task as Q/S/P
-- Does NOT read DECISIONS.md or IMPLEMENTATION_PLAN.md
-- Does NOT modify any files
-
-This is purely a workspace readiness check.