toolkit: no thread panic in http_fetch, no casts, exact egress-proxy form

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 |
 |---|---|---|---|---|---|---|---|
+| M3b/17-toolkit-nits | 2026-09-23 | done | 1 | pass | none | Three small fixes. `fetch.rs`: replaced `std::thread::spawn` with a `Builder::new().spawn` match that kills and waits on a spawn error and returns `Outcome::tool_error("http_fetch: cannot start a thread: {e}")`. `input.rs` and `files.rs`: replaced `MAX_INPUT as u64 + 1` / `MAX_READ as u64 + 1` with `u64::try_from(MAX_*).map_or(u64::MAX, |n| n.saturating_add(1))`. `main.rs` `parse_egress_proxy`: the first check is now `args.len() != 5 || args.first()?.as_bytes() != b"egress-proxy"` so a longer list goes to the tool form (exit 2). Copied `tests/egress_form.rs`; the one test failed before the fix and passed in 0.02s after. `grep "thread::spawn\| as u64" crates/toolkit/src/` prints nothing. `make gate` prints `gate: ok` first run. | ? |
 | M3b/16-brokerd-log-escaping | 2026-09-23 | done | 1 | pass | none | Escaped the container's standard error before logging it (M3b review finding 5) and prefixed/quoted three small texts (finding 7). `container.rs` `answer`: exit 2 logs `brokerd: {name}: the tool could not run: {err:?}` instead of the raw stderr; exit 125..=127 logs `brokerd: podman could not start {name}: {err:?}\n{RUNBOOK}` (was `{err}\n{RUNBOOK}`); the `_` arm logs `brokerd: container {name} exited {status}: {err:?}` (the trailing `\n{err}` moved inside the debug format). `start_egress`: the proxy's `podman run -d` failure now logs `{stderr:?}`. `main.rs`: the runtime notice prints `brokerd: {runtime_notice}`. `config.rs`: the image and memory `[runner]` errors use `{:?}` so the bad value is quoted. Copied `tests/container_log.rs` and `tests/notices.rs`; 4, 2, 2 and 7 passed; `make gate` prints `gate: ok` first run. | ? |
 | M3b/15-brokerd-pipes-grace | 2026-09-23 | done | 1 | pass | none | Fixed the two M3b review findings in `pipes.rs`. Added `pub const GRACE: Duration = Duration::from_secs(2)`; replaced the `JoinHandle`-holding `Io` with one holding `Option<Receiver<(Vec<u8>, bool)>>` for stdout/stderr and added the `Finished { out, truncated, err, open }` struct. `Io::start` now returns `std::io::Result<Io>`: the stdin writer is started with `Builder::new().spawn(...)` and its handle dropped (never joined, a spawn error returned with `?`); a new private `reader(pipe, cap) -> io::Result<Receiver<...>>` starts one detached reader per pipe and returns a spawn error, used for both stdout (`cap`) and stderr (`err_cap`). `Io::finish(grace)` sets one `until = Instant::now() + grace` and calls a private `collect(rx, until)` per receiver: `recv_timeout(until.saturating_duration_since(now))` → `Ok` keeps bytes, `Timeout` sets `open`, `Disconnected` (panicked reader) counts closed; `open` is `stdout_open || stderr_open`. `read_capped` unchanged in behavior, now `cap.saturating_sub(kept.len())` and `chunk.get(..take).unwrap_or_default()` (no indexing, no wrapping subtraction). `container.rs`: added `pub const OUTPUT_OPEN` after `TIMED_OUT`, `use crate::pipes::{GRACE, Io}`, and replaced the `run_container` tail with the task's `Io::start` match (on spawn error, `podman kill`/`rm -f`, `child.kill()`/`wait()`, log + `Unavailable(CANNOT_START)`), then `io.finish(GRACE)` and the `done.open && status.is_some()` check returning `Failed(OUTPUT_OPEN)` (a timed-out call, `status` None, still answers `TIMED_OUT`). All `std::thread::spawn` gone from `crates/brokerd/src/`. Copied `tests/container_grace.rs`; 4 passed in ~4.4s, container 11, container_egress 6, all five runs; `make gate` prints `gate: ok` first run. | ? |
 | M3b/14-brokerd-pipes-module | 2026-09-23 | done | 1 | pass | none | Pure move: cut `struct Io`, `impl Io { start, finish }`, and `fn read_capped` from `container.rs` and pasted them into `crates/brokerd/src/pipes.rs` with bodies unchanged and `pub(crate)` visibility; `Io::start` now calls `crate::container::STDERR_KEPT` (the constant stays in `container.rs` since the tests import it). Added the module doc comment and the `use std::io::{Read, Write}`, `use std::process::Child`, `use std::thread::JoinHandle` lines. `lib.rs` gained `pub mod pipes;` between `ledger` and `podman`. `container.rs` gained `use crate::pipes::Io;` and lost the `Read, Write` and `JoinHandle` imports the compiler reported unused; nothing else changed. `cargo fmt --all` reflowed the `STDERR_KEPT` call line in `start` to wrap. `cargo check`/clippy clean; container 11, container_egress 6, serve_runner 2 pass; `grep "struct Io\|fn read_capped" container.rs` prints nothing and `container.rs` is 350 lines. `make gate` prints `gate: ok` on the first run. | ? |