Add loopd configuration with every M2a limit

Implemented-By: Laguna S 2.1 (OpenCode)

docs/implementer-log.md

@@ -16,6 +16,7 @@ reviewer adds findings under "Reviews" once per milestone.
 | M1/09-gate-scripts-table-form | 2026-09-17 | done | 1 | pass | none | Rewrote check-lines, check-crate-deps and check-dep-docs to parse table-form (`[dependencies.x]`) and dotted (`x.path`) dependencies and to fail closed (exit 1 when crates/Cargo.toml/docs/dependencies.md is missing); check-lines now prints `file has N lines (limit 500)`. Self-test passes with 0 failures, all three scripts pass on the real tree, and `make gate` prints `gate: ok`. |
 | M2a/01-proto-sha256 | 2026-09-17 | done | 1 | pass | none | Added crates/proto/src/hash.rs wrapping emsha 1.0.4 (HashError, Sha256 with new/update/finish, sha256, Default); re-exported from lib.rs, added emsha workspace dep and dependencies.md row. One compile fix: finish needed `mut self` to call finalize. 4 hash tests pass, `make gate` prints `gate: ok`. |
 | M2a/02-inferproxy | 2026-09-17 | done | 3 | fail | none | Implemented Limits/TokenBucket/OpenGuard/serve/handle/forward in lib.rs (std only: the inference server's JSON is upstream's concern) and arg parsing + stale-socket handling in main.rs; TokenBucket counts thousandths of a token in u128 so partial refills stay additive and `saturating_duration_since` on an earlier `now` never underflows, capping at burst; serve refuses by rate-limit then open-connection limit; handle drops its OpenGuard before closing the client so a freshly-finished client is not refused on re-connect (rule 4). The scaffold `proto` dependency in `crates/inferproxy/Cargo.toml` was left untouched since the task's Modify/Copy lists cover only lib.rs, main.rs, the two test files and this log. First `make gate` failed on `clippy::map_clone` (`main.rs` used `.map(String::clone)`); switched to `.cloned()` and re-ran, then re-ran once more after restoring the proto scaffold — both pass. Hand test against straylight returned `{"status":"ok"}`; `forward.rs` passed 6/6 ten runs in a row. |
+| M2a/03-loopd-config | 2026-09-17 | done | 1 | pass | none | Wrote crates/loopd/src/config.rs: Config + Infer/Slots/Expect/Sampling/Limits with deny_unknown_fields on all six and struct-level `#[serde(deny_unknown_fields, default)]` on Sampling and Limits; manual Default impls for the two; hand-written Display/std::error::Error ConfigError named by file. Everywhere check: all six structs (Infer, Slots, Expect, Sampling, Limits, Config) carry deny_unknown_fields. One local fix: Display used `{path}` on a PathBuf and failed to build, switched to `path.display()`. 6 config tests pass; `make gate` prints `gate: ok`. |
 
 ## Reviews