feat(core): add opencode job_list, job_output, job_wait, and job_stop tools - #60497

Agents can now list, read live output from, wait on, and stop background jobs through tools.opencode.job_* without polling with sleep.
The four tools live in the opencode Code Mode catalog (codemode: true, pinned: true) so they stay out of the direct top-level tool list unless Code Mode is disabled. Stacked on #60495.

🔍 Origin: reported in #36423, #36424, and #56940

💡 Why: Once a build, server, Code Mode script, or subagent moved to the background, an agent had no way to inspect its live progress, wait boundedly when blocked on its output, or stop a stuck process (#36423, #36424, #56940) — and in a 120-run small-model eval across Haiku 5.5, DeepSeek V4.1 Flash, MiniMax M3, and Gemini 3.5 Flash Lite, putting job_* directly into top-level tool definitions caused smaller models to call job_output / job_wait with made-up IDs, whereas keeping them in tools.opencode.* produced 0 misfires (15/15 pass).

🆕 Now you can: Call tools.opencode.job_list, job_output, job_wait, and job_stop inside Code Mode (or as opencode_job_* when Code Mode is disabled), scoped strictly to jobs owned by the calling session.

+ tools.opencode.job_list({ status?: "running" | "all" }) // excludes the calling execute script itself
+ tools.opencode.job_output({ id })                       // live partial output or final settled output
+ tools.opencode.job_wait({ id, yield_after? })           // bounded wait (defaults to 10s)
+ tools.opencode.job_stop({ id })                         // cancels job (+ descendant jobs when stopping a subagent)

📊 Proof

New integration tests in packages/core/test/tool-job.test.ts fail without the change; 2 suites (17 assertions) pass.

👀 Read: packages/core/src/tool/plugin/job.ts in requireOwned and stopDescendantSessions — requireOwned rejects both foreign-session jobs and the active execute call's own callID so a script never lists or cancels itself. The rest is routine.