chore: migrate package manager from bun to pnpm

- Add pnpm-workspace.yaml for monorepo workspace
- Add root package.json with packageManager field
- Add .npmrc with shamefully-hoist=true
- Replace bun.lock with pnpm-lock.yaml
- Use workspace:* protocol for @uncaged/pulse dependency
- Update init.ts scaffold to use pnpm install
- Update CLI commands (tick/dev/deploy) to use pnpm/npx
- Update E2E test comments to reference pnpm
- Keep bun as TS runtime (bun:sqlite, bun:test still needed)

closes #19

package.json

@@ -1,5 +1,7 @@
 {
+  "name": "pulse-monorepo",
   "private": true,
+  "packageManager": "pnpm@10.33.0",
   "scripts": {
     "lint": "biome check packages/",
     "lint:fix": "biome check --write packages/"