build-skill-references.ts: import regex is blind to multi-line imports, under-reporting skill schema deps

[os-zhuang]

Found while fixing generated-skill drift in #3138 — out of scope there (it is pre-existing and identical before/after regeneration, so it does not affect that diff), filed per Prime Directive #10.

Problem

packages/spec/scripts/build-skill-references.ts resolves the transitive schema closure with a single-line regex:

const re = /^import\s+.*\s+from\s+['"](\.[^'"]+)['"]/gm;

. does not match newlines, so a multi-line import is never seen:

import {
  FooSchema,
} from './foo.zod';        // ← invisible to the resolver

The dep is silently omitted from the skill's "Transitive dependencies" section. No warning — the file simply never enters the queue.

Impact

18 non-test multi-line local imports in packages/spec/src are currently invisible, e.g.:

api/feed-api.zod.ts       -> ../data/feed.zod
api/feed-api.zod.ts       -> ../data/subscription.zod
api/protocol.zod.ts       -> ./analytics.zod
api/protocol.zod.ts       -> ../kernel/package-registry.zod
automation/bpmn-mapping.ts -> ./control-flow.zod
integration/connector/*.zod.ts -> ../connector.zod   (×4)

(217 including .test.ts, which are irrelevant here.)

The effect is under-reporting, not a broken pointer: skills/*/references/_index.md ships to third parties via npx skills add, and an agent following the index gets an incomplete picture of the schema graph. Whether any of the 18 is reachable from a SKILL_MAP entry's closure is worth checking — that determines real-world impact.

Second, related blind spot

extractLocalImports appends .ts only when the specifier does not already end in .ts:

if (!resolved.endsWith('.ts')) resolved += '.ts';

So a .js-suffixed ESM specifier resolves to foo.js.ts, never exists, and is dropped — e.g. contracts/data-engine.ts -> ../data/index.js and conversions/apply.ts -> ./types.js.

Suggested fix

Replace the regex with a real import scan (TS AST, or at minimum a multi-line-tolerant pattern plus .js → .ts specifier normalization). Note this will legitimately grow the "Transitive dependencies" section of several indexes — a gate now guards those files (#3138), so the regen must land with the fix.

Why this is safe to do now

#3138 added check:skill-refs, proven to fail on stale/missing/leftover output, so any change to the resolver will surface as drift rather than rot silently.