feat(cli): add browser_task tool

[iscekic]

What changed

• The CLI exposes a browser_task tool that sends a goal to the user's browser extension and returns the result in the chat.
• The tool returns a summary, evidence when available, a terminal status, and a task ID.
• Calling the tool again with the task ID continues that browser conversation. It does not resend the goal or the CLI transcript.
• The caller must name one enabled, connected browser provider. The tool never falls back to another provider.
• A long task returns an accepted job with a task ID and a hint to check progress later. It does not hold the request open.
• A task settles with an honest terminal status on timeout, provider loss, or disconnect.
• A repeated submit of the same logical task reuses one invocation ID, so the server dedupes instead of starting a duplicate run.
• The task owner comes from the authenticated connection, never from a model argument.
• The tool fails closed until the browser_tasks.enabled setting is set, and it stays hidden when the session is not connected.

Why

The browser extension already hosts a browser agent. The CLI needs a way to delegate a goal to it and receive the result, without hosting the agent in the CLI, adding a second transport, or changing mobile. The requirements demand per-profile queueing, continuation by task ID, honest settlement, reconnect recovery with dedupe, and an owner derived from authentication.

Verification

• Driver checks: per-slice checks passed.
• Backend session-ingest check passed.
• CLI test:ci failed only on files that also fail on clean main (pre-existing); advisory.
• Extension chrome e2e passed.

Notes for the reviewer

• The diff adds a stray test helper at packages/opencode/test/kilocode/runner-tree-71132-1788260372845.test.ts. It spawns a sleep process, writes a PID marker, and throws when KILO_TEST_RUNNER_PID_FILE is unset. Remove it before merge.