Add the loopd serve command

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

docs/implementer-log.md

@@ -37,6 +37,7 @@ reviewer adds findings under "Reviews" once per milestone.
 | M2b/05-loopd-session | 2026-09-18 | done | 2 | fail | none | Copied the given test byte-identical and wrote crates/loopd/src/session.rs: `Session` (id, dir, baseline, records, appended log file, next_call) and `SessionError` (Exists/NotFound/Io/Torn/Baseline/Encode) with derived Debug, Display and std::error::Error::source. `create` refuses an existing dir, writes `0.baseline.json`, opens `0.jsonl` with `create_new`+`append`, and appends a `SessionStart` (`Timestamp::now()`, epoch 0, the slot, `baseline.hash()`). `open` reads the baseline from the file (not `system.md`), requires every log line to end in `\n` and parse as a `LogRecord` else `Torn` with the 1-based line and reason, and sets `next_call` to one past the highest `ToolResult` call. `append` encodes, writes, `sync_data()`, then pushes to memory. All 7 session tests pass. First gate failed on clippy: split the `source()` arm that bound three different error types into three arms, removed the redundant `.write(true)` (implied by `append`), and used `path.display()` for the `Torn` path. | ? |
 | M2b/06-loopd-turn | 2026-09-18 | done | 1 | pass | none | Wrote crates/loopd/src/turn.rs (299 lines) and registered `pub mod turn;` in lib.rs; copied the two given tests and three fixtures byte-identical. `TurnError` (SessionFull/TurnLimit/Infer/Session, Display + std::error::Error + From<SessionError>), `TurnOutcome`, `Runtime`, `is_context_full` (the one 400 whose JSON `error.type` is `exceed_context_size_error`), and `run_turn`: append User, build the ChatRequest (slot, messages, tools, thinking), capture `last_usage`, `chat_with_retry` mapping ChatEvent->TurnEvent (dropping ToolCallDelta), append Assistant then Usage, report cache loss between the two conversations, and on no tool calls return `TurnOutcome { content: completion.content.unwrap_or_default(), usage }`; otherwise iterate tool calls under the iteration cap with a repeated-call detector (first repeat returns "already called", a second repeat is TurnLimit), `cap_result`, and `dispatch` (find_tool/call_tool local, every other tool — including read_file — to the port). `run_call` maps Dispatch::Local and every ToolResponse variant to (text, Public, untrusted). Two compile fixes before the gate: `u64::try_from(*ahead).unwrap_or(u64::MAX)` (usize has no From<u64>) and `let Ok(value) = from_str(body) else { return false }` (a temporary borrow); `session.baseline()` returns a reference so it is bound inside the loop. All 6 turn and 9 limits tests pass; `make gate` prints `gate: ok`. | ? |
 | M2b/07-loopd-channel | 2026-09-18 | done | 3 | fail | none | Wrote crates/loopd/src/channel.rs and registered `pub mod channel;` in lib.rs. `Context` holds a private `Mutex<HashSet<SessionId>>`; `serve` accepts forever with one thread per connection and returns on an accept error; `handle` does the seven steps (read_frame with Closed-before-anything, turn-only, mark busy, open-or-create plus run_turn streaming events, release before the final frame, error-code mapping, quiet write failure). The busy guard is a `Held` struct that borrows the context immutably and holds a clone of the id but never the lock, and it is dropped before sending turn_done or error so a client can send the next turn the moment it reads the last one — that is what keeps `a_busy_session_is_refused_at_once` and the concurrent-session test correct. Channel test reported `6 passed` ten runs in a row, all clean. Two fixes before a clean gate: `cargo fmt` import order and a clippy `question_mark` on the accept loop, re-run after each. | ? |
+| M2b/08-loopd-serve | 2026-09-18 | done | 2 | fail | none | Rewrote crates/loopd/src/main.rs into two commands, `selftest` and `serve`, both sharing `run_selftest_check` so the self-test lines are identical. `serve` loads config (exit 1 on failure), removes an existing socket via `channel_socket()` before the self-test, runs the self-test and exits 1 without binding on failure, then creates the socket's parent dir, binds, sets mode 0600 with `std::fs::set_permissions`, prints `serving on`, and calls `channel::serve` with a `Context` from the config, client, `Box::new(FakeTools::new())` and `Registry::m2b()`. Anything else prints both usages and exits 2. The `serve_refuses...` test's "no socket left behind" holds because the socket is removed before the self-test and binding happens only after it passes. First gate run failed on two clippy `collapsible_if` lints; collapsed the two nested `if let` into edition-2024 let-chains and re-ran, which passed. `cargo test -p loopd --test serve` reports 3 passed. | ? |
 
 
 ## Reviews