Add typed tool arguments and the form checks for paths, hosts and URLs

Implemented brokerd::args: a pure module (no I/O, no clock) that parses tool
arguments into a typed ToolArgs and checks the form of paths, hosts and URLs.
Four private deny_unknown_fields structs drive parse and canonical_json; path,
cwd and url are validated as written and never normalised. All 13 args tests
pass and make gate prints gate: ok.

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

docs/implementer-log.md

@@ -45,7 +45,8 @@ reviewer adds findings under "Reviews" once per milestone.
 | M3a/02-proto-admin-wire | 2026-09-22 | done | 1 | pass | none | Added four DenyReason (GrantsInvalid, AuditUnavailable, InvalidArguments, StateUnreadable), two ErrorCode (Forbidden, NoSuchApproval), approval ids as u64 in ToolResponse::PendingApproval and TurnEvent::ApprovalPending, TurnEvent::ApprovalPending and ToolDenied, and the eight admin types (Empty {}, PendingApproval, ApprovalList, Approve, ApproveResult, Refuse, GrantProblem, GrantsReport) with deny_unknown_fields; re-exported from lib.rs; added the two required match arms in bxctl chat.rs. Copied four test files and 17 wire fixtures byte-identical. wire 10, turn_wire 5, admin_wire 10, strict 5 passed; `make gate` prints `gate: ok`. | OpenCode |
 | M3a/01-proto-audit-types | 2026-09-22 | done | 1 | pass | none | Finished the blocked task. `audit.rs` now holds the chained shapes: `DecisionRecord` (`Allowed {}`, `Ask {}`, `Denied { reason }`), `ApprovalAnswer`, `ResultStatus`, `AuditEvent` (Decision/Approval/Result/Recovery/AcceptedBreak), and `AuditRecord { seq, time, prev, event }`; `lib.rs` re-exports the five names. All `Option`s emit as `null` (no `skip_serializing_if`); `deny_unknown_fields` on all three object enums/struct. Tests copied from `docs/plans/M3a/files/`: `records` 3 passed, `strict` 5 passed. Proved the brace rule has teeth: with `Allowed`/`Ask` as unit variants, `audit_records_reject_unknown_keys_at_every_depth` accepted `{"outcome":"allowed","zz_unknown":true}` and failed; braces restored, it passes again. NOTE: `docs/plans/M3a/files/crates/proto/tests/strict.rs` was already locally modified in the working tree (the committed version walks 16 wire fixtures that do not exist on m3a and are created by task 02) — I copied it as-is from the path, which is why `strict` is 5 passed; I did not touch any other protected file. `git status` was not empty at start because of that pre-existing modification, which I left uncommitted and unstaged. | OpenCode |
 | M3a/03-proto-chain-verifier | 2026-09-19 | done | 1 | pass | implementation matches the reference tree's chain.rs verbatim |
-| M3a/04-brokerd-config | 2026-09-18 | done | 1 | pass | none | Wrote crates/brokerd/src/config.rs: Paths (Default: home is $BOXMAKER_HOME via var_os else /var/lib/boxmaker, grants /etc/boxmaker/grants), Sockets (derived Default), Approvals (Default ttl_ms 900_000) and Config (derived Default), all with serde(deny_unknown_fields, default) and Config at top level; hand-written ConfigError Read/Parse with Display and std::error::Error; parse/load/broker_socket/admin_socket/audit_dir/state_dir. Added serde, serde_json, toml to Cargo.toml, `pub mod config;` to lib.rs, and `brokerd` to the serde and serde_json "Used by" cells in dependencies.md. 7 config tests pass; `make gate` prints `gate: ok`. | OpenCode | Wrote crates/proto/src/chain.rs: `ChainVerifier`, a pure line-holding state machine (each line is judged only once the next one has arrived, so a `Recovery` record can mark the line before it not-a-record), plus `ChainFailure`, `TornTail`, `ChainReport`, `Location`. Holds each line, checks recovery against the next, then rule 1 (parse, expected seq, prev with the file-before text for line 1 of a resumed/continued verifier), the failed-region counting of rule 5, the resumed-earlier-file break exception of rule 6, run/ask tracking for `abandoned`/`unfinished`, and clock warnings; `finish` reports the torn tail and the break's required seq/prev. Added `pub mod chain` and the five re-exports to lib.rs and the same line to audit.rs. The single worker subagent for this task entered an unrecoverable reasoning loop on the state machine and was not completing, so the orchestrator implemented it directly from the spec and fixtures. 13 chain tests pass; `make gate` prints `gate: ok`. | OpenCode |
+| M3a/04-brokerd-config | 2026-09-18 | done | 1 | pass | none | Wrote crates/brokerd/src/config.rs: Paths (Default: home is $BOXMAKER_HOME via var_os else /var/lib/boxmaker, grants /etc/boxmaker/grants), Sockets (derived Default), Approvals (Default ttl_ms 900_000) and Config (derived Default), all with serde(deny_unknown_fields, default) and Config at top level; hand-written ConfigError Read/Parse with Display and std::error::Error; parse/load/broker_socket/admin_socket/audit_dir/state_dir. Added serde, serde_json, toml to Cargo.toml, `pub mod config;` to lib.rs, and `brokerd` to the serde and serde_json "Used by" cells in dependencies.md. 7 config tests pass; `make gate` prints `gate: ok`. | OpenCode |
+| M3a/05-brokerd-args | 2026-09-23 | done | 4 | fail | none | Wrote crates/brokerd/src/args.rs (MAX_PATH, MAX_URL, ToolName with ALL/parse/as_str, ToolArgs with tool/canonical_json, ArgsError with hand-written Display+Error, parse, valid_path, inside, valid_host, valid_host_pattern, host_matches, url_host) and added `pub mod args;` to lib.rs. 13 args tests pass; `make gate` prints `gate: ok`. Three clippy fixes before a clean gate: collapsed the shell `cwd` if-let into an edition-2024 let-chain, `('a'..='z').contains` -> `is_ascii_lowercase`, and the trailing `/` match -> `?`. `source()` returns None because `String` does not implement `std::error::Error`. The URL rules read the host as written (no `to_lowercase`); uppercase fails `valid_host`, matching the test that lists `https://Example.com/` as invalid. | OpenCode | Wrote crates/proto/src/chain.rs: `ChainVerifier`, a pure line-holding state machine (each line is judged only once the next one has arrived, so a `Recovery` record can mark the line before it not-a-record), plus `ChainFailure`, `TornTail`, `ChainReport`, `Location`. Holds each line, checks recovery against the next, then rule 1 (parse, expected seq, prev with the file-before text for line 1 of a resumed/continued verifier), the failed-region counting of rule 5, the resumed-earlier-file break exception of rule 6, run/ask tracking for `abandoned`/`unfinished`, and clock warnings; `finish` reports the torn tail and the break's required seq/prev. Added `pub mod chain` and the five re-exports to lib.rs and the same line to audit.rs. The single worker subagent for this task entered an unrecoverable reasoning loop on the state machine and was not completing, so the orchestrator implemented it directly from the spec and fixtures. 13 chain tests pass; `make gate` prints `gate: ok`. | OpenCode |
 
 
 ## Reviews