fix: wire worktree flag into hermes CLI entry point + docs + tests

Critical fixes:
- Add --worktree/-w to hermes_cli/main.py argparse (both chat
  subcommand and top-level parser) so 'hermes -w' works via the
  actual CLI entry point, not just 'python cli.py -w'
- Pass worktree flag through cmd_chat() kwargs to cli_main()
- Handle worktree attr in bare 'hermes' and --resume/--continue paths

Bug fixes in cli.py:
- Skip worktree creation for --list-tools/--list-toolsets (wasteful)
- Wrap git worktree subprocess.run in try/except (crash on timeout)
- Add stale worktree pruning on startup (_prune_stale_worktrees):
  removes clean worktrees older than 24h left by crashed/killed sessions

Documentation updates:
- AGENTS.md: add --worktree to CLI commands table
- cli-config.yaml.example: add worktree config section
- website/docs/reference/cli-commands.md: add to core commands
- website/docs/user-guide/cli.md: add usage examples
- website/docs/user-guide/configuration.md: add config docs

Test improvements (17 → 31 tests):
- Stale worktree pruning (prune old clean, keep recent, keep dirty)
- Directory symlink via .worktreeinclude
- Edge cases (no commits, not a repo, pre-existing .worktrees/)
- CLI flag/config OR logic
- TERMINAL_CWD integration
- System prompt injection format

website/docs/reference/cli-commands.md

@@ -22,6 +22,7 @@ These are commands you run from your shell.
 | `hermes chat --provider <name>` | Force a provider (`nous`, `openrouter`, `zai`, `kimi-coding`, `minimax`, `minimax-cn`) |
 | `hermes chat --toolsets "web,terminal"` / `-t` | Use specific toolsets |
 | `hermes chat --verbose` | Enable verbose/debug output |
+| `hermes --worktree` / `-w` | Start in an isolated git worktree (for parallel agents) |
 
 ### Provider & Model Management