daemon: fold CORE's confirms into the engine-API review

CORE resolved all four (lane/core@3da4cd6): vdm::TaskId is hashable and
DAEMON never constructs one; DAEMON mkdir -p's save_path's parent
(engine -> Error::path_rejected if missing); sha512 added as the 4th
Checksum::Algo so no -32602 at the RPC edge; on_state(cancelled) then
on_finished(Err{Error::canceled}) -- note the one-L spelling in the
error taxonomy. Also notes rate/token_bucket + Engine::rate_limiter()
for the limiter.set wiring.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Upd9WhG9oppieig5nRDLig

daemon/docs/engine-api-review.md

@@ -62,24 +62,28 @@ and it is already `DownloadSpec.mirrors` + the segmenter's 3-failure requeue, no
 segments to the new URL from their current offsets; if they don't match, surface it
 (`on_decision_needed` or a `refresh_url` error) rather than silently restarting.
 
-## To confirm — none block sign-off
+## Confirmed by CORE (`lane/core@3da4cd6`)
 
-1. **`vdm::TaskId` ↔ wire UUID.** `sched/` keeps a `vdm::TaskId → wire taskId` map, keyed
-   off `handle.id()` at `start()`. Confirm `vdm::TaskId` is cheap to copy and hashable
-   (`std::unordered_map` key), and that DAEMON is never expected to *construct* one — it
-   only ever receives them from `start()` / callbacks and passes them back to
-   `set_task_order()`.
-2. **Parent directory creation.** The engine "never canonicalises or root-checks"
-   `save_path` — does it `mkdir -p` the parent (the category folder may not exist yet), or
-   must DAEMON ensure the directory exists before `start()`? DAEMON assumes the latter
-   (it owns category/path logic) unless you say otherwise.
-3. **`Checksum::Algo` has no `sha512`**, but `Checksum.schema.json` accepts it (PROTO F3).
-   DAEMON will reject `algorithm: "sha512"` at the RPC edge with `-32602` before `start()`
-   unless CORE would rather carry a fourth enum value. Either is fine; say which.
-4. **`on_finished(Err{cancelled})`** — DAEMON keys on `ErrorInfo.code == cancelled` to
-   write a `cancelled` history row rather than surfacing it as a user-facing failure.
-   Confirm `cancelled` is the code and that `on_state(_, cancelled, nullopt)` always
-   precedes it (the §4 table implies this).
+1. **`vdm::TaskId`** — cheap-copy and `std::hash`-able; DAEMON never constructs one, only
+   receives it from `start()` / callbacks and passes it back to `set_task_order()`.
+   `sched/` keeps the `vdm::TaskId → wire taskId` map keyed off `handle.id()`.
+2. **Parent directory** — DAEMON `mkdir -p`s `save_path`'s parent before `start()`; the
+   engine opens the file and fails the task with `Error::path_rejected` if it is missing.
+   Now explicit on `DownloadSpec`'s doc comment.
+3. **`sha512`** — added as the fourth `Checksum::Algo`, matching the wire set. No `-32602`
+   at the RPC edge; DAEMON passes it straight through.
+4. **Cancel ordering** — `on_state(_, cancelled, nullopt)` then `on_finished`, always in
+   that order. Note the taxonomy value is spelled `canceled` (one L): the finish is
+   `on_finished(Err{Error::canceled})`, `error.code == canceled`. `sched/` keys on that
+   to write a `cancelled` history row rather than a user-facing failure. (The wire
+   `TaskState` / `EngineState` spelling stays `cancelled`; only `vdm::Error` is one-L.)
+
+## Related, landed the same pass
+
+`rate/token_bucket` — the global → queue → task speed-limiter hierarchy (`docs/04` §6),
+reached via `Engine::rate_limiter()`. DAEMON's `limiter.set {globalBps, enabled}` maps to
+`rate_limiter().set_global_limit(...)`; `limiter.get` reads it back. Wire this alongside
+the `download.add` → `start()` glue.
 
 ## Integration timing