simulate: fail fast and clearly for Node agents that can't run simulations

[u9g]

Two ways lk agent simulate dead-ends Node agent users, with no hint at the cause.

1. @livekit/agents 1.0.0–1.4.9 pass the version check, then die. The CLI's Node floor is 1.0.0. Simulate, though, starts the agent with --simulation and LIVEKIT_AGENT_NAME_OVERRIDE, and both first shipped in 1.4.11 (1.4.10 was never published). On 1.4.9 the user gets the agent exited before registering. Agent output: error: unknown option '--simulation'. Projects created from agent-starter-node before 2026-06-30 pin ^1.4.7, often held there by a lockfile. Simulate now checks for 1.4.11 and says @livekit/agents version 1.4.9 is too old, please upgrade to 1.4.11 or newer. The shared 1.0.0 floor for dev/start/console is unchanged, since those commands don't use either flag.

2. A Node agent that crashes in entry() shows only "No agent joined room". Broken-agent detection matched only Python log lines. A throwing Node entrypoint left every job to time out at 30s, and the real error stayed in the temp agent log. The 3-scenario starter can never reach the more-than-3 "not joined" threshold, so the run always played out in full. Adding agents-js's error in entry function (job_lifecycle.ts) to the markers lets the existing path cancel the run and print the error.

Repro (starter Node agent, CI=1 lk agent simulate text --scenarios scenarios.yaml --yes):

• @livekit/agents 1.4.9: main prints unknown option '--simulation'. This branch prints the upgrade message.
• throw new Error("boom: missing API key") at the top of entry(): main took 73–92s, with 3 of 3 jobs failing on No agent joined room. This branch cancelled within 9–18s and printed error in entry function: boom: missing API key.

The broken-agent path still exits 0 in CI on main. That's fixed separately in #1047.

Commits: a pure refactor that makes the version check take the floor as a parameter, then one commit per fix. go test ./cmd/lk/ passes.

[u9g]

Before/after on a Node agent. With @livekit/agents 1.4.9, main dies on unknown option '--simulation' and this branch asks the user to upgrade to 1.4.11. When entry() throws, main spends 73s on three No agent joined room timeouts; this branch cancels in 9s and shows the agent's real error.

node-sim.mp4