fix(dts-plugin): handle EXIT before dev server init

[BleedingDev]

Summary

• Prevent a crash when the dev-worker receives an EXIT RPC message before ModuleFederationDevServer is initialized.
• Extract message handling into handleDevWorkerMessage so the behavior is deterministic and testable.
• Keep existing runtime behavior for initialized servers (still calls moduleServer.exit() then exits process).

Why

In some startup/teardown races, the process message listener can receive RpcGMCallTypes.EXIT before moduleServer is assigned.
The previous implementation called moduleServer.exit() unconditionally, which can throw and skip normal process shutdown flow.

Changes

• packages/dts-plugin/src/dev-worker/forkDevWorker.ts
  • Delegate message handling to a helper and pass current moduleServer + fileLog.
• packages/dts-plugin/src/dev-worker/handleWorkerMessage.ts
  • Add a small pure handler with guarded moduleServer?.exit() behavior.
• packages/dts-plugin/src/dev-worker/handleWorkerMessage.spec.ts
  • Add regression coverage for:
    • EXIT before server init
    • EXIT with initialized server
    • non-EXIT messages

Validation

• pnpm nx run dts-plugin:lint
• pnpm --filter @module-federation/dts-plugin exec vitest run src/dev-worker/handleWorkerMessage.spec.ts
• bun --bun -e "import { handleDevWorkerMessage } from './packages/dts-plugin/src/dev-worker/handleWorkerMessage.ts'; let code=-1; handleDevWorkerMessage({ type: 'mf_exit', id: 'bun-smoke' }, { processExit: (c) => { code = c ?? -1; }, log: () => {} }); console.log(code === 0 ? 'ok' : 'bad');"

All pass locally.

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Latest commit: 33dd994

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Bundle Size Report

1 package(s) changed, 37 unchanged.

Package	Total dist	Delta	ESM gzip	Delta
dts-plugin	627.5 kB	+818 B (+0.1%)	23.4 kB	no change

Total dist: 6.67 MB (+818 B (+0.0%))
Total ESM gzip: 137.6 kB (no change)