fix: bootstrap DTO class erasure + wizard failure + port prefill + Pi SDK copy (IUV-M01, #436)

- Bug 1 [CRITICAL]: drop `import type` on BootstrapSetupDto in bootstrap.controller.ts
  so NestJS preserves the class reference for design:paramtypes; ValidationPipe now
  correctly validates the DTO instead of 400ing on every field.
  Add e2e integration test (bootstrap.e2e.spec.ts) via @nestjs/testing + supertest
  that exercises the real DI/Fastify binding path to guard against regressions.
  Configure vitest to use unplugin-swc with decoratorMetadata:true.

- Bug 2: remove `&& headlessRun` guard in wizard.ts so bootstrap failure (completed:false)
  aborts with process.exit(1) in both interactive and headless modes — no more
  silent '✔ Wizard complete' after a 400.

- Bug 3: add `initialValue` to WizardPrompter.text() interface, ClackPrompter, and
  HeadlessPrompter; use it in gateway-config.ts promptPort() so 14242 prefills the
  input buffer and users can press Enter to accept. Apply same pattern to other
  gateway config prompts (databaseUrl, valkeyUrl, corsOrigin).

- Bug 4: add Pi SDK to the 'What is Mosaic?' intro copy in welcome.ts.

- Bump @mosaicstack/mosaic 0.0.25 → 0.0.26.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/mosaic/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@mosaicstack/mosaic",
-  "version": "0.0.25",
+  "version": "0.0.26",
   "repository": {
     "type": "git",
     "url": "https://git.mosaicstack.dev/mosaicstack/mosaic-stack.git",