⚡️ refactor: Migrate @librechat/api build to tsdown (#13595)

* ⚡️ refactor: Migrate @librechat/api build to tsdown

Replace Rollup with tsdown (rolldown + oxc isolated-declarations) for the
@librechat/api package build, mirroring the merged data-schemas migration.

- Add tsdown.config.mjs (cjs output, oxc dts, externalize all bare deps,
  bundle first-party `~/` + relative imports)
- Annotate exports for isolatedDeclarations (codefix-driven). Collapse the
  tokens.ts model->token maps to Record<string, Record<string, number>> and
  switch validation.ts's runtime `files` field from z.any() to z.unknown()
  so no explicit `any` is introduced
- Repoint package.json main/types/exports to tsdown's .cjs/.d.cts output
- Add src/telemetry.ts entry shim so the two index.ts entries don't collide
  in oxc's flat dts output (stable dist/telemetry.{cjs,d.cts})
- Delete rollup.config.js

Build time ~36s -> ~0.5s. No runtime behavior change: 5712 unit tests pass,
both entries load via require(), legacy /api consumes them unchanged.

* 👷 ci: Hash packages/api/tsdown.config.mjs in build-api cache keys

The build-api cache keys hashed `packages/api/server-rollup.config.js`,
which never existed (api used `rollup.config.js`, now removed) — a copy-paste
artifact from the data-provider key that matched no file. Replace it with the
new `packages/api/tsdown.config.mjs` so edits to the build config (entry,
format, externals) bust the api build cache, matching the data-schemas key.

.github/workflows/backend-review.yml

@@ -68,7 +68,7 @@ jobs:
         uses: actions/cache@v4
         with:
           path: packages/api/dist
-          key: build-api-${{ runner.os }}-${{ hashFiles('packages/api/src/**', 'packages/api/tsconfig*.json', 'packages/api/server-rollup.config.js', 'packages/api/package.json', 'packages/data-provider/src/**', 'packages/data-provider/tsconfig*.json', 'packages/data-provider/rollup.config.js', 'packages/data-provider/package.json', 'packages/data-schemas/src/**', 'packages/data-schemas/tsconfig*.json', 'packages/data-schemas/tsdown.config.mjs', 'packages/data-schemas/package.json') }}
+          key: build-api-${{ runner.os }}-${{ hashFiles('packages/api/src/**', 'packages/api/tsconfig*.json', 'packages/api/tsdown.config.mjs', 'packages/api/package.json', 'packages/data-provider/src/**', 'packages/data-provider/tsconfig*.json', 'packages/data-provider/rollup.config.js', 'packages/data-provider/package.json', 'packages/data-schemas/src/**', 'packages/data-schemas/tsconfig*.json', 'packages/data-schemas/tsdown.config.mjs', 'packages/data-schemas/package.json') }}
 
       - name: Build api
         if: steps.cache-api.outputs.cache-hit != 'true'

.github/workflows/config-review.yml

@@ -70,7 +70,7 @@ jobs:
         uses: actions/cache@v4
         with:
           path: packages/api/dist
-          key: build-api-${{ runner.os }}-${{ hashFiles('packages/api/src/**', 'packages/api/tsconfig*.json', 'packages/api/server-rollup.config.js', 'packages/api/package.json', 'packages/data-provider/src/**', 'packages/data-provider/tsconfig*.json', 'packages/data-provider/rollup.config.js', 'packages/data-provider/package.json', 'packages/data-schemas/src/**', 'packages/data-schemas/tsconfig*.json', 'packages/data-schemas/tsdown.config.mjs', 'packages/data-schemas/package.json') }}
+          key: build-api-${{ runner.os }}-${{ hashFiles('packages/api/src/**', 'packages/api/tsconfig*.json', 'packages/api/tsdown.config.mjs', 'packages/api/package.json', 'packages/data-provider/src/**', 'packages/data-provider/tsconfig*.json', 'packages/data-provider/rollup.config.js', 'packages/data-provider/package.json', 'packages/data-schemas/src/**', 'packages/data-schemas/tsconfig*.json', 'packages/data-schemas/tsdown.config.mjs', 'packages/data-schemas/package.json') }}
 
       - name: Build api
         if: steps.cache-api.outputs.cache-hit != 'true'

.github/workflows/playwright-mock.yml

@@ -79,7 +79,7 @@ jobs:
         uses: actions/cache@v4
         with:
           path: packages/api/dist
-          key: build-api-${{ runner.os }}-${{ hashFiles('package-lock.json', 'packages/api/src/**', 'packages/api/tsconfig*.json', 'packages/api/server-rollup.config.js', 'packages/api/package.json', 'packages/data-provider/src/**', 'packages/data-provider/tsconfig*.json', 'packages/data-provider/rollup.config.js', 'packages/data-provider/package.json', 'packages/data-schemas/src/**', 'packages/data-schemas/tsconfig*.json', 'packages/data-schemas/tsdown.config.mjs', 'packages/data-schemas/package.json') }}
+          key: build-api-${{ runner.os }}-${{ hashFiles('package-lock.json', 'packages/api/src/**', 'packages/api/tsconfig*.json', 'packages/api/tsdown.config.mjs', 'packages/api/package.json', 'packages/data-provider/src/**', 'packages/data-provider/tsconfig*.json', 'packages/data-provider/rollup.config.js', 'packages/data-provider/package.json', 'packages/data-schemas/src/**', 'packages/data-schemas/tsconfig*.json', 'packages/data-schemas/tsdown.config.mjs', 'packages/data-schemas/package.json') }}
 
       - name: Build api
         if: steps.cache-api.outputs.cache-hit != 'true'