## What changed
Add `Client::activate` to load a cloud thread through `UpdateConfig`, sending only the thread ID and `exclude_turns=true`. Return serializable resolved settings, thread metadata, and history cursors while leaving turns for separate pagination. Preserve the original thread protobuf, including unknown fields.
Validate required fields and thread identity, reject unsupported security policies, and redact sensitive activation data in debug output. Treat activation as a mutation that is never retried, with uncertain outcomes reported through `MutationError::OutcomeUnknown`.
## Testing
Add coverage for activation request encoding, settings and metadata preservation, serialization, compatibility defaults, unsupported policies, debug redaction, invalid input rejection, and explicit successful gRPC trailers.
GitOrigin-RevId: cd925b7a05f518d782e5b4cf188556567dad9e21
## What changed
Add `codex-cloud-client`, a reusable Rust client for `ThreadService.Resume` and live `ThreadService.Attach` over HTTP/2. Callers supply the native gRPC origin, bearer token, account ID, and `HttpClientFactory`.
- Reuse shared proxy, custom CA, and network policy handling for HTTPS. Reject redirects and allow plaintext HTTP only on direct loopback with unrestricted, unmanaged policy.
- Preserve notification and server-request protobuf payloads as opaque bytes and expose native gRPC status details while redacting credentials, payloads, and error details from diagnostics.
- Bound resume and attach setup to 150 seconds without retrying requests or imposing an idle deadline on live streams. Attach ends on its first error and provides no history or automatic reconnect.
- Select Rustls in `HttpClientBuilder::http2_prior_knowledge()` so HTTPS advertises `h2` through ALPN.
Include a standalone attach example and documentation of admission semantics and stream behavior.
## Testing
Add HTTP/2 fixture tests for protobuf framing, authentication metadata, status trailers, event preservation, malformed responses, stream cancellation, redirect rejection, and diagnostic redaction. Add checks for unsafe origins, network policy restrictions, and TLS `h2` advertisement.
GitOrigin-RevId: 55db70438bb5e59272c6995c67a46ced5fa28ff4