feat(session): support Node.js agents in the local session daemon

[toubatbrian]

Important

Depends on / must wait for: livekit/agents-js#1706 — feat(console): console CLI runner + AgentsConsole session wiring (text mode).

The Go daemon spawns the JS agent with node <entry> console --connect-addr <addr>. The JS console --connect-addr TCP runner that accepts this is added in agents-js#1706, which is not yet merged. The underlying TcpSessionTransport (agents-js#1693) is already merged, but without #1706 there is no JS console TCP entrypoint to dial the daemon. Do not merge this until agents-js#1706 lands.

Summary

Extends the lk agent session local daemon to drive Node.js/TypeScript agents, not just Python. Previously Node projects were rejected at project-detection time; this wires up the Node spawn path so a JS/TS agent is driven over the exact same text-mode console protocol (console --connect-addr <addr>) as Python.

Changes

• cmd/lk/agent_utils.go — detectProject no longer gates on Python-only. It now also accepts Node projects (already recognized by DetectProjectRoot via package.json) and the error message reflects both supported runtimes.
• cmd/lk/simulate_subprocess.go — extracted interpreter/argv resolution into buildAgentCommand, branching on project type:
  • Python: <python> <entry> <args> (uv prefixes run python)
  • Node: node [--experimental-strip-types] <entry> <args>
  • Added findNodeBinary (resolves node from PATH) and isTypeScriptEntry so a .ts/.mts/.cts entrypoint runs directly via Node's type-stripping loader — no build step required.
• cmd/lk/session_daemon.go — dropped the stale TODO(node); the daemon now spawns either runtime via buildConsoleArgs.

Underlying spawned command

node --experimental-strip-types <entry> console --connect-addr 127.0.0.1:<port>

(--experimental-strip-types is added only for TypeScript entrypoints.)

Test plan

Verified end-to-end against a JS agent (@livekit/agents, with agents-js#1706 checked out locally):

• lk agent session start examples/src/console_text_agent.ts — detects the Node project, spawns the JS agent, connects to the Go TCP console server, completes the text-mode handshake (Session started.)
• lk agent session say "What is the weather in Tokyo?" — round-trips a turn including a getWeather function-tool call and the agent reply
• Second turn ("And what about Paris?") — multi-turn confirmed
• lk agent session end — clean shutdown
• Python path unchanged (argv resolution refactor preserves prior behavior)

Note: lk agent session is text-mode only; this PR does not touch the audio/voice lk agent console path.

Dependencies

• feat(console): console CLI runner + AgentsConsole session wiring (text mode) agents-js#1706 — JS console CLI runner (console --connect-addr). Required; merge after this lands.
• feat(voice): add TcpSessionTransport and updateIo session handler agents-js#1693 — TcpSessionTransport + updateIo handler (already merged).