script/check: also run source-map-check so doc-coverage failures surface during iteration

Two stories landed at the merge gate today (961, 962) with everything
else green, killed by a single missing `///` doc comment. The merge
gate runs source-map-check; script/check (and therefore the
mcp__huskies__run_check tool that coders use during iteration) did
not. So coders only saw the failure when the merge gate fired —
minutes after they thought they were done.

Chain source-map-check after cargo check so every iteration loop
catches a missing `///` instantly. AGENT.md already calls this out as
a required pre-commit step; making it part of the fast feedback loop
removes the "I forgot" failure mode.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

script/check

@@ -1,5 +1,8 @@
 #!/usr/bin/env bash
-# Fast compile-only check: no frontend build, no clippy, no tests.
+# Fast compile-only check + doc-coverage check on changed files.
 # Use this for rapid iteration feedback while writing code.
+# Catches the doc-coverage gate failures locally instead of waiting for
+# the merge gate to bounce on a single missing `///`.
 set -euo pipefail
 cargo check --tests --workspace
+cargo run -p source-map-gen --bin source-map-check -- --worktree . --base master