fix(ship): branch off HEAD without stashing

ship.py stashed the working tree, created the branch off `main`, then popped
the stash back. When the current branch's docs.json had diverged from main (e.g.
running on a feature branch mid-restructure), the pop conflicted, crashed the
step, and left conflict markers committed into the docs — while stranding the
user's real work in a dangling stash.

Branch off the CURRENT HEAD instead and drop the stash entirely: the promoted
changes already in the working tree carry over with no conflict, and unrelated
uncommitted work is never touched. On main (CI, the intended context) HEAD == main,
so behavior is unchanged; on a divergent branch it now succeeds safely instead of
corrupting state.

Verified by reproducing the divergent scenario: branch created off HEAD, docs
committed, no stash, exit 0.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: shirgoldbird

pipeline/ship.py

@@ -212,7 +212,7 @@ def main():
     need_new_branch = current_branch != branch_name
 
     if need_new_branch:
-        print(f"  Will create branch: {branch_name} (off main)")
+        print(f"  Will create branch: {branch_name} (off {current_branch})")
     else:
         print(f"  On branch: {branch_name}")
 
@@ -242,17 +242,19 @@ def main():
         return 0
 
     # --- Create branch ---
+    # No stashing. Branch off the CURRENT HEAD so the promoted changes already in
+    # the working tree carry over cleanly. The old approach stashed the working
+    # tree and popped it onto a branch created off `main`; when the current
+    # branch's docs.json had diverged from main, that pop conflicted, crashed the
+    # step, and left conflict markers in the tree. Branching off HEAD applies with
+    # no conflict and never disturbs unrelated uncommitted work.
     if need_new_branch:
         if branch_exists(branch_name):
             print(f"Switching to existing branch: {branch_name}")
-            run(["git", "stash", "push", "-m", "pipeline-ship"])
             run(["git", "checkout", branch_name])
-            run(["git", "stash", "pop"])
         else:
-            print(f"Creating branch: {branch_name} (off main)")
-            run(["git", "stash", "push", "-m", "pipeline-ship"])
-            run(["git", "checkout", "-b", branch_name, "main"])
-            run(["git", "stash", "pop"])
+            print(f"Creating branch: {branch_name} (off {current_branch})")
+            run(["git", "checkout", "-b", branch_name])
 
     # --- Stage and commit ---
     print("Staging docs files...")