Bump workspace to 0.13.1. Inter-crate path deps synced in lockstep
(17 pins across 9 crates/*/Cargo.toml, 0.13.0 -> 0.13.1). CHANGELOG
[0.13.1] section confirmed.

Features carried in this release:
- fix(git): git_cmd / git_cmd_combined async migration with tokio
  timeout wrap (root fix for MCP server hang under network git
  subcommand). Commits 64e72de + 2661ced.
- refactor(git,session): externalize worktrees dir via
  SessionConfig::worktrees_dir + env LDS_WORKTREES_DIR + default
  <root>/.worktrees (backward compatible). Commit b5d0a78.

Note: publish-checker Phase 6 Convention Leak Gate flags .worktrees
literal as a false positive against Outline private-convention-tokens
Tokens node — .worktrees is this crate's public API namespace, not
internal leak. Human override per project-owner authority; SoT-side
Public API Exemptions restore is a follow-up carry.

Release Manifest: workspace/releases/0.13.1.md (gitignored).