docs(openspec): gate 123 lets a check leave the floor only through sigrid.yaml

openspec/changes/gate-123-sig-floor/design.md

@@ -27,7 +27,11 @@ For each floored check the head misses:
 | missed (only possible via the file) | worse | FAIL: it erodes a floor development already breaks |
 | missed | not worse | inherited: printed, not counted |
 
-A check that disappears from the head (its language left the measured scope) fails, because nothing proves it is still met. A pull request that removes a check from the floor file fails as well.
+A check that disappears from the head (its language left the measured scope) fails, because nothing proves it is still met, unless the same pull request changes `sigrid.yaml` (Ruben, 2 November 2026). An explicit scope change may take checks out of the floor and out of the floor file in that pull request. A check the base no longer measures either left in an earlier pull request and is not judged again.
+
+A pull request that removes a check that is still measured from the floor file fails, with or without a `sigrid.yaml` change.
+
+Without a floor file the gate is NOT APPLICABLE before it loads a tool or resolves a base, so a missing tool never turns an app without a floor into SKIPPED (wiring).
 
 Inherited breaches exist only after an admin merge past a red gate. They do not fail unrelated pull requests, in line with the inherited-debt rule; development fixes them forward.
 

openspec/changes/gate-123-sig-floor/specs/gate-sig-floor/spec.md

@@ -73,3 +73,20 @@ The gate SHALL measure exactly what gate 122 measures, including the app's `sigr
 - **GIVEN** `sigrid.yaml` excludes `lib/Generated/`
 - **WHEN** a pull request adds a 74-line unit there
 - **THEN** the gate passes
+
+### Requirement: A check leaves the floor only through sigrid.yaml
+
+A floored check the head no longer measures SHALL fail the gate, unless the same change edits `sigrid.yaml` or `sigrid.yml`, or the base does not measure it either. A change that edits `sigrid.yaml` MAY remove the checks it takes out of scope from the floor file. Removing a check that is still measured SHALL fail.
+
+#### Scenario: A language leaves without a scope change
+
+- **GIVEN** the floor lists `javascript unit_size >15`
+- **WHEN** a pull request deletes the app's only JavaScript file
+- **THEN** the gate fails with `javascript unit_size >15: no longer measured`
+
+#### Scenario: An exclude in sigrid.yaml
+
+- **WHEN** a pull request adds `.*/src/.*` to `sigrid.yaml` and removes the JavaScript checks from the floor file
+- **THEN** the gate passes and reports the checks as having left the scope through sigrid.yaml
+- **AND** the next pull request is not judged on them
+

openspec/changes/gate-123-sig-floor/tasks.md

@@ -20,4 +20,4 @@
 
 ## 4. Adoption
 
-- [ ] 4.1 One pull request per fleet app with `.github/sig-floor.json` from its development head, together with `hydra-gates-sig-blocking: true`
+- [x] 4.1 One pull request per fleet app with `.github/sig-floor.json` from its development head, together with `hydra-gates-sig-blocking: true`