fix(taskfile): remove build targets for binaries deleted months ago, and make check build

Closes #120 (items 2 and the suggested gate fix).

`task build` has been broken since `cmd/supervisor` was deleted in c117634, and
CI stayed green the entire time. That combination is the finding: not that a
path went stale, but that nothing could notice.

`check` ran lint, test and vet. All three walk `./...`, which enumerates the
packages that EXIST. A build target naming a DELETED package is invisible to
every one of them — `go vet ./...` cannot complain about a directory it never
visits. The gate was complete with respect to the code present and blind to the
code referenced.

`build` is now part of `check`, with that reasoning written above it.
Flip-tested: reintroducing `go build ./cmd/supervisor` takes `task check` to
exit 201, naming the missing directory.

Removed, all pointing at binaries that no longer exist:

- `supervisor:dev` and `supervisor:build`     -> ./cmd/supervisor
- `supervisor:test:smoke`                     -> curls a server nothing can start
- `smoke:routing` + scripts/smoke-routing.sh  -> ./cmd/routing
- the `supervisor:` line in Procfile, which also still pointed
  SUPERVISOR_MODELS_FILE at the file deleted in #116

`build` now aggregates `hyperguild:build` + `ingestion:build`, the two binaries
that actually exist.

A false lead worth recording so it is not re-investigated: a first sweep flagged
`./cmd/server` and `./cmd/frontmatterlint` as missing too. They are not — their
tasks set `dir: ingestion`, and both exist under `ingestion/cmd/`. Any checker
for this class has to resolve a task's working directory before judging its
paths, or it reports two false positives for every true one.

Not addressed here: #120's third item, that `internal/config` has zero non-test
callers. `RoutingConfig` is the only written record of the routing pod's
configuration contract, so deleting it is a judgement call rather than a
correction.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Procfile

@@ -1,2 +1 @@
 ingestion: cd ingestion && INGEST_BRAIN_DIR=../brain INGEST_PORT=3300 INGEST_WATCH_INTERVAL=30 go run ./cmd/server/
-supervisor: SUPERVISOR_CONFIG_DIR=./config/supervisor SUPERVISOR_MODELS_FILE=./config/models.yaml SUPERVISOR_SESSIONS_DIR=./brain/sessions INGEST_BASE_URL=http://localhost:3300 INGEST_SVC_URL=http://localhost:3300 go run ./cmd/supervisor/