feat: add Git worktree compatibility (PR #478)

Adds comprehensive Git worktree support for beads issue tracking:

Core changes:
- New internal/git/gitdir.go package for worktree detection
- GetGitDir() returns proper .git location (main repo, not worktree)
- Updated all hooks to use git.GetGitDir() instead of local helper
- BeadsDir() now prioritizes main repository's .beads directory

Features:
- Hooks auto-install in main repo when run from worktree
- Shared .beads directory across all worktrees
- Config option no-install-hooks to disable auto-install
- New bd worktree subcommand for diagnostics

Documentation:
- New docs/WORKTREES.md with setup instructions
- Updated CHANGELOG.md and AGENT_INSTRUCTIONS.md

Testing:
- Updated tests to use exported git.GetGitDir()
- Added worktree detection tests

Co-authored-by: Claude <noreply@anthropic.com>
Closes: #478

integrations/beads-mcp/pyproject.toml

@@ -6,8 +6,8 @@ readme = "README.md"
 requires-python = ">=3.10"
 license = {text = "MIT"}
 dependencies = [
-    "fastmcp==2.14.0",
-    "pydantic==2.12.5",
+    "fastmcp==2.13.1",
+    "pydantic==2.12.4",
     "pydantic-settings==2.12.0",
 ]
 authors = [