feat(cli): add --reload-dir to dev for extra watch directories

[korya]

Problem

dev-mode auto-reload only watches the entrypoint, livekit.agents, and editable plugins. Edits to other packages the agent imports (shared utility code mounted editable in monorepos) are silently ignored — the worker keeps holding stale module objects with no warning.

Solution

Add repeatable --reload-dir (and LIVEKIT_RELOAD_DIRS, os.pathsep-split) to dev. Resolved paths are unioned with the auto-discovered list and passed to the existing watchfiles.arun_process. Auto-discovery is unchanged; omitting the flag preserves identical behavior.

flowchart LR
    F["--reload-dir / LIVEKIT_RELOAD_DIRS"] --> CA[CliArgs.reload_dirs]
    AD[_find_watchable_paths<br/>main + livekit.agents + plugins] --> U[union]
    CA --> U
    U --> AP["watchfiles.arun_process(*paths,<br/>watch_filter=PythonFilter())"]

Loading

Naming mirrors uvicorn's --reload-dir so muscle memory transfers.

Notes worth flagging

• Missing path fails fast (exit 1, clear error). Silent skip would re-create the gap this PR closes.
• PythonFilter is retained, so .git/, .venv/, __pycache__/, node_modules/, and non-.py files don't trigger reloads — even inside user-supplied dirs.
• The flag does not split on commas (A,B → single path). Only the env var splits on os.pathsep. Help text calls this out.
• No allowlist gating (/, ~, paths above cwd): hard-rejecting outside cwd would break the very monorepo workflow this is for, and PythonFilter already drops the dangerous dirs.

Test plan

tests/test_reload_dir.py — 16 scenarios:

• Defaults, repeated flag, env-var split, flag-overrides-env
• Relative + ~ paths, symlink resolution
• Missing path (flag + env) → exit 1
• CliArgs pickle round-trip
• iTerm2 carve-out preserved (with and without --reload-dir)
• WatchServer.run() unions auto + user paths, keeps PythonFilter
• PythonFilter drops .git/HEAD, .venv/*.py, etc.
• tests/test_cli_log_level.py (25 cases) still passes

Manual: dev --help shows the flag + env-var; dev --reload-dir /tmp/extra logs Watching /tmp/extra (user); bad path → exit 1.

Changeset: .github/next-release/changeset-reload-dir.md (livekit-agents minor).

🤖 Generated with Claude Code

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

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