feat(git-pilot): implement v2 with rebase, worktrees, stash, and agent teams

[moukrea]

Summary

Major upgrade to git-pilot implementing six new features from the v2 technical specification:

• Branch freshness detection: auto-fetch on session start, fast-forward behind branches, warn on divergence
• Base branch drift detection: detect when the base branch has advanced, auto-rebase before push with configurable conflict strategy
• Intelligent rebase & conflict resolution: structured conflict details with recommendations, tri-state protectDefaultBranch (warn/block/off)
• Unrelated work detection: UserPromptSubmit hook provides branch context so Claude can detect off-topic requests
• Agent Teams support: suppress interactive prompts for spawned agents, orchestrator-only operations, git worktree management
• Automatic stash management: auto-stash/restore on branch switches

Changes

• 3 new library scripts: agent.sh, rebase.sh, worktree.sh
• 1 new hook: prompt-context.sh (UserPromptSubmit)
• 6 modified hooks: session-start, session-stop, pre-commit, post-bash, post-write, hooks.json
• 3 new skills: /stash, /worktree, /rebase
• 3 modified skills: /branch, /finish, /configure
• Updated config schema: 13 new config keys across rebase, worktree, agentTeams sections
• CLAUDE.md: expanded from 6 to 10 rules
• Plugin version: 1.1.0 → 2.0.0
• Test suite: 74 bats test cases across 9 test files

Test plan

• bash -n plugins/git-pilot/scripts/*.sh passes (verified)
• shellcheck --severity=warning plugins/git-pilot/scripts/*.sh passes (verified)
• jq . plugins/git-pilot/defaults/config.json valid (verified)
• jq . plugins/git-pilot/hooks/hooks.json valid (verified)
• All 7 skills have valid YAML frontmatter
• CLAUDE.md contains all 10 rules and 7-skill reference table
• v1 config files remain backward compatible (boolean protectDefaultBranch normalized)
• Run bats plugins/git-pilot/tests/ for full test suite