ci(api): the committed openapi.generated.ts has drifted ~1,000 lines from docs/openapi.yaml, and nothing checks it

[alex-dembele]

Problem

A frontend developer, or a client built from our types, reads frontend/src/types/openapi.generated.ts as the contract of the API. On 2026-09-25 that file no longer matches docs/openapi.yaml: npm run generate:api-types changes it by +950 / −39 lines. Nothing in CI regenerates it or compares it, so the drift only grows, and type-check stays green on types that are out of date.

Reproduction:

cd frontend && npm ci
npm run generate:api-types
git diff --stat -- src/types/openapi.generated.ts
# 1 file changed, 950 insertions(+), 39 deletions(-)

Related: #630 (ten activation routes missing from openapi.yaml) and #602 (verified as resolved; this drift was found while checking it).

Acceptance criteria

1. The generated file is regenerated and committed. npm run type-check and npm run lint:ceiling stay green, and any type error the regeneration surfaces is fixed in the same PR.
2. A blocking CI step runs generate:api-types and fails if git diff --exit-code -- frontend/src/types/openapi.generated.ts is not empty.
3. CONTRIBUTING.md says in one line that editing openapi.yaml means regenerating the types.

Definition of Done

A PR that changes docs/openapi.yaml without regenerating the types is red in CI. The CI output of a deliberately failing test is pasted here.