weichen
fcd2539b9e
Why: the completion doc requires the client to recognize resultType, treat input_required as a protocol-level result whose answer retries the original tools/call, and expose tasks/get|update|cancel; today only a content-block special case existed and the advertised version was never checked against the server's. Evidence: GOWORK=off go vet + go test -count=1 ./... green; TestInputRequiredResultTypeRetriesOriginalCall (ask → tasks/update → retry, call order and final content), TestNegotiatedVersionFallbackKeepsLegacyPath (byte-level legacy behavior on 2024-11-05), TestTasksGetAndCancelRoundTrip, TestRunEndCancelsSeenTasks, TestDefaultSchemaDeclares202012; the acceptance-③ regression TestStdioSlowCancelThenEcho passes unchanged. Impact: advertise 2026-07-28 and branch on the negotiated version (older servers keep byte-identical behavior); synthesized default tool schemas now declare JSON Schema 2020-12; runs cancel the MCP tasks they saw via a per-run TaskTracker (other runs on the shared manager are unaffected). Refs: Agent-System-Documents#42 (N2 plan WP3)