summary

• replace fake v2 prompt/compact/wait successes with a typed session operation-unavailable failure
• map unfinished v2 session mutations to public 503 ServiceUnavailableError responses
• document and test the new OpenAPI error contracts

testing

• bun test test/server/httpapi-session.test.ts test/server/httpapi-public-openapi.test.ts
• bun typecheck
• bun test ./test/server/httpapi-exercise/index.ts
• bun turbo typecheck