The Run state machine was removed in MR-771 (v0.4.0); `docs/dev/runs.md`
and `crates/omnigraph/tests/runs.rs` have since documented and tested the
direct-publish write path, so the "runs" name was misleading.
- git mv docs/dev/runs.md → docs/dev/writes.md (reframe H1 + intro;
keep MR-771 history note)
- git mv crates/omnigraph/tests/runs.rs → tests/writes.rs (reframe header)
- repoint every runs.md / runs.rs reference across docs, AGENTS.md, and
source comments
- fix four pre-existing broken `docs/runs.md` links (the file never lived
at that path) to `docs/dev/writes.md`
- fix the stale v0.4.0 anchor to the live section
No behavior change: every source edit is a comment. Engine builds and the
renamed test passes 25/25; scripts/check-agents-md.sh passes.
The run-removal cleanup itself (run_registry.rs guard, __run__ prefix) is
deferred to MR-770.
