hil: rename the HIL contract to hil-contract and keep only TinyUSB's mechanics (#4225)

* hil: rename the HIL contract to hil-contract and keep only TinyUSB's mechanics

agentrc's hil skill now holds the rules every project shares (locks,
running, reporting, verdicts, retries); this page keeps hosts and
rosters, selection, build receipts, local and remote execution,
reservation, results, recovery and limits under its eight sections.
Requires hathach/agentrc#83.

* hil-contract: hold other projects' names separately and list what the report hides

* hil-contract: name the usbtest failure line without its colored status

* hil-contract: name the reply's skipped and usbtest fields and state the usbtest retry rule once

* hil-contract: scope the operator retry to test failures and classify usbtest aborts and filtered tests

* hil-contract: keep the first retry attempt, classify usbtest aborts by cause and scope the retry per variant

* hil-contract: gate the retry on a blocker row, classify unlisted usbtest aborts and list a re-run regression

* hil-contract: keep retried for a locked retry, decide a pass-then-fail row by its re-run and pin the roster skip line

* hil-contract: fold the enumerated usbtest blocker lines into the did-not-run default

* hil-contract: allow retried {} when no retry ran

* hil-contract: keep the extraction to the harness's output and name what it hides

Revert the operator-authored reply fields and the retry and verdict rework to the first commit's wording, keeping the separate cross-project hold. State what the report cannot show (#4226), the fail-open lock dir, the exit mapping, what an empty selection leaves uncovered and a failed flash's FAIL cell.

* hil-contract: point the shared lock and retry rules at hil and list the report's folds in Limits