fix(metadata): the /library subpath needs an index.ts, or scripts/ typechecks against dist

`tsconfig.scripts.json` maps `@metaobjectsdev/metadata/*` to
`packages/metadata/src/*` so the repo-root `scripts/` typecheck reads workspace
SOURCE — its own comment says so, and the reason is that a bare import and a
relative import to the same file would otherwise be two class declarations.

`/library` was the one subpath with no `index.ts` to land on: `/core` has one,
the root entry has one, and `package.json` pointed `/library` straight at
`library-sources.ts`. So the mapping missed, tsc fell through to `node_modules`,
and found `dist/library/library-sources.d.ts`. That file exists on a machine that
has built and does not exist on a fresh checkout, where the `gates` lane runs
`bun install` and never builds. Hence green here, `TS2307` × 4 there.

`--traceResolution` before: `src/library/index.ts` does not exist → node_modules.
After: `src/library/index.ts` exists - use it as a name resolution result. The
fallback is never reached, so the result no longer depends on a warm `dist/`.

`package.json` now names the index for all three conditions, which is what every
other subpath does. The exported surface is unchanged — both modules were loaded
and their key sets compared, and the eleven names are identical.

The gate's own instruction is "fix the error; do not widen this gate", so nothing
in `tsconfig.scripts.json` moved.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011cQxyVuTkdPmAduLiedNEg

Author: dmealing

server/typescript/packages/metadata/package.json

@@ -17,9 +17,9 @@
       "default": "./dist/core/index.js"
     },
     "./library": {
-      "bun": "./src/library/library-sources.ts",
-      "types": "./dist/library/library-sources.d.ts",
-      "default": "./dist/library/library-sources.js"
+      "bun": "./src/library/index.ts",
+      "types": "./dist/library/index.d.ts",
+      "default": "./dist/library/index.js"
     },
     "./constants": {
       "bun": "./src/constants.ts",

server/typescript/packages/metadata/src/library/index.ts

@@ -0,0 +1,17 @@
+// @metaobjectsdev/metadata/library — the shipped-library surface (FR-043).
+//
+// Every other subpath of this package resolves through a directory `index.ts`
+// (`/core`, and the root entry itself). This one pointed straight at
+// `library-sources.ts`, and that inconsistency was not cosmetic: the repo-root
+// `tsconfig.scripts.json` maps `@metaobjectsdev/metadata/*` to
+// `packages/metadata/src/*` so that `scripts/` typechecks against workspace
+// SOURCE rather than a build output. With no `index.ts` here that mapping had
+// nothing to land on, so resolution fell through to `node_modules` and found
+// `dist/library/library-sources.d.ts` — which exists on a developer's machine
+// and does NOT exist on a fresh CI checkout, where the `gates` lane runs
+// `bun install` and never builds. The gate was green locally and red on the
+// runner for exactly that reason.
+//
+// So this file is the subpath's entry, and `package.json` names it. Adding a
+// module under `library/` means re-exporting it here.
+export * from "./library-sources.js";