P6 during the run: split the runner task (02 core, 03 workers); guard.PreCheck as an owner commit; AGENTS.md: write code into files early

Task 02 (the whole runner) ended at 21:08 with no file and no commit: Ornith wrote the
implementation out in its reply (~700 lines), OpenCode compacted the session, and the model
then emitted a malformed tool call. It had also looked for the given test at a wrong path
("_files/…" relative to the plan: my ambiguity).

- 02-runner → 02-runner-core (types, Submit, Status, Touch, Cancel; no goroutines) and
  03-runner-workers; the given test split to match (runner_core_test.go gains three tests:
  queued storage, cancel while queued, Status never moves the lease); later tasks renumbered
  04-09 and every cross-reference checked.
- Copy paths spelled from the repo root.
- guard.PreCheck (+ its test) is committed here by the owner: the old task 05 told the
  implementer to edit internal/guard/, which AGENTS.md forbids. My contradiction.
- AGENTS.md rule 6: write code into files early, in small steps.
Both runner test files compile against a panic-only skeleton (the core file also alone) and
fail there on panic: todo.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

AGENTS.md

@@ -18,6 +18,10 @@ Go and runs on orion under a hardened systemd unit. You are implementing it one
    only that file, and tell the owner.
 5. Work only from files inside this repository. Never read another checkout, and never search the
    file system for code. If you are stuck, stop as in point 4.
+6. **Write code into files early and in small steps.** Start each new file with its types and
+   signatures, make it compile, then fill in one function at a time and run the tests as you go.
+   Never write a whole implementation out in your reply before putting it in a file: a long
+   session is compacted, and what was only in the reply is lost (P6 task 02, 2026-09-26).
 
 ## Files you must never edit