Docs: three stale claims in ARCHITECTURE.md and FORMAT.md (benchmark report, worker container, check list)

Three claims in ARCHITECTURE.md and FORMAT.md have drifted from reality. Each fix is a sentence. ## 1. The benchmark report is described as future work, but it shipped - `docs/ARCHITECTURE.md:95` says "our benchmark report will publish what we measure" and `docs/ARCHITECTURE.md:244` says "A benchmark report (tracked in issues) will publish what the simple version achieves". - `docs/FORMAT.md:29` says "measured defaults are a benchmark-report deliverable" and `docs/FORMAT.md:74` says "configurable defaults pending the benchmark report". - Reality: `docs/BENCHMARKS.md` exists and publishes exactly those results. Every other page already links it (`docs/README.md`, `docs/FAQ.md`, `README.md`, `docs/RUNTIME.md`); ARCHITECTURE.md and FORMAT.md are the only pages that never do. - Fix: switch the four sentences to present tense and link `./BENCHMARKS.md`. ## 2. There is no worker container - `docs/ARCHITECTURE.md:135` says the Compose bundle is "Airflow 3.x services + Postgres + a worker container". - Reality: the bundle uses LocalExecutor with no separate worker. See the service list in `src/hflow/runtime/_templates.py` (postgres, airflow-init, user-venv-init, apiserver, scheduler, dag-processor, triggerer; "No Redis, no Celery worker") and the correct table already in `docs/RUNTIME.md:54`. - Fix: replace "+ a worker container" with the actual arrangement, for example "no separate worker container: LocalExecutor runs tasks in the scheduler". ## 3. The built-in check list omits `action_rate` - `docs/ARCHITECTURE.md:179` enumerates the built-in checks and says "Two of the classic cuts are corpus-relative judgments...: `episode_duration` ... and `content_digest`". - Reality: `src/hflow/checks.py` ships seven public checks, and `action_rate` (`src/hflow/checks.py:338`) is exactly the same corpus-relative species; `docs/CATALOG.md` already queries `action_rate_hz` in its cohort-statistics example. - Fix: add `action_rate` to the sentence (three corpus-relative cuts, not two). ## Definition of done - All four benchmark-report sentences read as present tense and link `./BENCHMARKS.md`. - ARCHITECTURE.md no longer claims a worker container and matches RUNTIME.md. - The check list names `action_rate`. - Line numbers above are from current main; re-check them before editing. ## Validation ```bash lychee --no-progress --include-fragments \ --exclude '^https://github\.com/Hebbian-Robotics/hflow/(issues|security/advisories/new)$' \ --exclude-path references/mcap-spec.md \ --exclude-path references/foxglove-CompressedVideo.proto . ```