gatewayd: deliver, turns on loop.sock and answers posted in their thread

Implemented-By: OpenCode session (model recorded in docs/implementer-log.md)

docs/implementer-log.md

@@ -6,6 +6,7 @@ reviewer adds findings under "Reviews" once per milestone.
 
 | Task | Date | Status | Gate runs | First gate | Deviations | Notes | Model |
 |---|---|---|---|---|---|---|---|
+| M4a/13-gatewayd-deliver | 2026-09-23 | done | 1 | pass | none | Copied `tests/deliver.rs`, `tests/support/fake_loop.rs` and the `src/deliver.rs` skeleton, added `pub mod deliver;` to `lib.rs` (before `http`, alphabetical). Filled `error_text` (the snake_case name serde gives the ErrorCode via `serde_json::to_value`, falling back to `<unknown>` without ever formatting `ErrorCode` with `{}` since it has no Display); `split_answer` (blank/whitespace-only → [EMPTY_ANSWER]; else while the rest is longer than `MAX_POST` *characters*, cut at the last newline within the first `MAX_POST` chars past position 0 — dropping that newline — else at the byte index of the `MAX_POST`-th char via `char_indices().nth(MAX_POST)`, never inside one char); `one_turn` (connect fails → LoopDown("cannot connect to <path>: <e>"), write one id-1 final Turn envelope (write error → LoopDown), then read: (1, not final, TurnEvent)→on_event, (1, final, TurnDone)→Answer(content), (1, final, Error)→Refused, a read error → LoopDown("the turn ended early: <e>"), anything else → LoopDown("an unexpected frame")); `run_turn` (one_turn with `batch.resume`, and when Refused(NoSuchSession) with `batch.resume` true, one more with resume false to create the session, as `bxctl chat --session`); `deliver` (post in the thread — ApprovalPending posts `approval_text` at once, then Answer→every split part in order, Refused→error_text, LoopDown→log "gatewayd: <session>: <why>" and post LOOP_DOWN; a failing post logs "gatewayd: cannot post in <channel> (thread <root>): <e>" through a small `post` helper). All 9 tests pass; `make gate` prints `gate: ok` first run. | ? |
 | M4a/12-gatewayd-state | 2026-09-23 | done | 1 | pass | none | Copied `tests/state.rs` and the `src/state.rs` skeleton, added `pub mod state;` to `lib.rs`. Filled `problem` (every `channels` key, `recent` and `threads` entry must be `valid_id` → "not a Mattermost id: <id with {:?}>"; each `in_flight` entry, session `mm-`+valid id with channel and root valid → "a turn in flight is not valid: <session with {:?}>"); `load` (NotFound → empty StateFile, any other read error, serde parse error or `problem()` → Read(path, why)); `save`/`persist` (the six atomic steps of brokerd's persist, io error mapped to Write, old file left on failure); `handled` (records unseen ids keeping the newest RECENT_KEPT, moves the channel mark to the max), `mark` (sets only a channel without a mark), `join_thread` (keeps the newest THREADS_KEPT), `start_turn`/`end_turn`/`take_in_flight` (removing by session, save only when in_flight was non-empty). Every mutating method saves before returning. All 4 tests pass in ~0.04 s; `make gate` prints `gate: ok` first run. | ? |
 | M4a/11-gatewayd-sessions | 2026-09-23 | done | 2 | fail | Removed the `resume` field from the copied `Pending` struct (written by the skeleton but never read) | Filled `named` (byte scan for `@`, the longest run of ASCII alnum/`.` `-` `_` after it, trailing `.` trimmed, lower-cased, empty runs skipped, then continue past the name) and the `Router` (`route` is a straight line of early returns in spec order: own -> Ignore(Own); kind not empty -> System; user not in allow.users -> NotAllowed; then the channel where "D" is always ours and "O"/"P"/"G" needs an allowed channel id plus `for_us`; the thread root is `root_id` or the post id; `!!...` keeps one `!` and queues, a lone `!` or `!approve`/`!deny` is a command where approve/deny answers M4B_COMMAND and anything else UNKNOWN_COMMAND, a command never reaches loopd; then Queue with session `mm-<root>`, `resume = root_id not empty`, `joins_thread = channel_type != "D"`). `for_us` is true when it names this bot (case-insensitive), otherwise a reply in a known thread that names only channel/here/all. `Queues`: `push` starts a turn when idle (Start with that message alone), waits while running and returns Full(thread) at the limit; `finish` joins the waiting texts with "\n\n" as a resume:true Batch, clears the queue and stays running, removing the session when nothing waits. `Pending.resume` was dead code (the next turn is always a continuation so `finish` hardcodes resume:true) so I removed it rather than allow a lint. First gate failed on clippy `manual_strip`; switched `starts_with("!!")`/`starts_with('!')` plus `&message[2..]`/`&message[1..]` slicing to `strip_prefix`. All 8 sessions tests pass; `make gate` prints `gate: ok` on the second run. | ? |
 | M4a/10-gatewayd-mm | 2026-09-23 | done | 1 | pass | none | Copied `tests/mm_json.rs`, `tests/mm_rest.rs` and `tests/support/http_server.rs`, added the `src/mm/mod.rs` and `src/mm/rest.rs` skeletons to `crates/gatewayd/src/mm/` and `pub mod mm;` to `lib.rs` (before `secrets`, alphabetical). Filled `mod.rs`: `Post::check` requires `id`/`user_id`/`channel_id` `valid_id` and `root_id` empty-or-`valid_id`, else `Json` quoting the offending id with `{:?}`; `json` is `serde_json::from_slice` mapped to `Json(e.to_string())`; `parse_event` matches `hello`/`posted`/other — `posted` takes `data.post` as a JSON *string* (an object or missing is `Json`), parses it, `check`s it, and reads `data.channel_type` (else ""), any other name (or an empty-name reply) is `Other(name)`; `typing` is `serde_json::json!` compacted; `since_list` walks `order` only (skipping ids not in `posts`, keeping `create_at > since && delete_at == 0` after `check`, deduping, then sorting by `(create_at, id)`), `full` when `order.len() >= SINCE_LIMIT`. Filled `rest.rs`: `Client::new` stores the three fields; `once` connects within `timeout`, sets the read timeout, sends `Authorization: Bearer <token>` (the only `expose`), `Accept`/`Content-Type` headers and `host_header`, mapping every error to `Net("<method> <path>: <e>")`; `call` loops `once` — 2xx returns the body, 401/403 `Auth`, 429 waits `rate_limit_wait` up to `RETRIES` then `RateLimited`, 5xx retried up to `RETRIES` times sleeping `RETRY_5XX`, else `Status` with the first `BODY_KEPT` lossy-UTF-8 chars via a `status_error` helper; `me`/`create_post`/`posts_since`/`direct_channel` build the four calls, `posts_since` and `me`/`direct_channel` reject non-`valid_id` ids as `Json` before sending. All 7 `mm_json` and 10 `mm_rest` tests pass (the latter ~3 s on two deliberate rate-limit waits); `make gate` prints `gate: ok` first run. | ? |