Exclude Bun example from pnpm workspace

[petyosi]

Summary

• Exclude examples/nextjs-bun from the pnpm workspace because it is a standalone Bun example with its own bun.lock.
• Regenerate the root pnpm-lock.yaml so frozen pnpm installs no longer validate that example's pinned published dependency.
• Prevent Changesets version PRs from bumping the example's pinned @pydantic/logfire-browser dependency before the new package version exists on npm.

Root Cause

The merged Version Packages PR bumped examples/nextjs-bun/package.json from @pydantic/logfire-browser@0.16.2 to 0.16.3, but the root pnpm-lock.yaml still contained the 0.16.2 importer. GitHub Actions then failed during Setup Vite+ because vp install runs with a frozen lockfile in CI.

Verification

• vp install --frozen-lockfile
• vp run --filter "./packages/*" build
• vp check
• vp run --filter "./packages/*" typecheck
• vp run --filter "./packages/*" test