feat(claude/commands): add rebase command

Automate rebasing onto upstream default branch with auto-stash,
conflict resolution, and clean abort/restore on low confidence.

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

claude/commands/rebase.md

@@ -0,0 +1,33 @@
+---
+allowed-tools: Bash(git fetch:*), Bash(git rebase:*), Bash(git stash:*), Bash(git diff:*), Bash(git log:*), Bash(git add:*), Read, Edit
+description: Rebase current branch onto upstream main/master
+---
+
+## Context
+
+- Current branch: !`git branch --show-current`
+- Default branch: !`git remote show origin | sed -n 's/.*HEAD branch: //p'`
+- Uncommitted changes: !`git status --short`
+
+## Your Task
+
+Rebase the current branch onto the upstream default branch (main or master).
+
+1. If there are uncommitted changes, stash them first with
+   `git stash push -m "auto-stash before rebase"`.
+2. Fetch the latest from origin: `git fetch origin`.
+3. Rebase onto the default branch using the value from context above:
+   `git rebase origin/<default-branch>`.
+4. If the rebase succeeds and changes were stashed in step 1, run
+   `git stash pop`.
+5. Show the result with `git log --oneline -10`.
+
+If the rebase fails due to conflicts, attempt to resolve them yourself.
+If you have low confidence in the resolution, abort the rebase with
+`git rebase --abort`, restore any stashed changes with `git stash pop`,
+and ask the user to resolve manually — leaving the working tree as it
+was found.
+
+You have the capability to call multiple tools in a single response. Do not
+use any other tools or do anything else. Do not send any other text or
+messages besides these tool calls.