Add CI workflow to auto-update rolldown stats on main branch changes

[Copilot]

This PR adds a new GitHub Actions workflow that automatically updates rolldown build statistics whenever changes are pushed to the main branch that modify the dashboard code.

What it does

The new .github/workflows/update-rolldown-stats.yml workflow:

• Triggers automatically when code is pushed to the main branch with changes to apps/dashboard/**
• Runs performance analysis using the existing pnpm rolldown:stats command
• Commits results back to main if the statistics file changes

Why this is needed

The dashboard directly imports and visualizes rolldown performance data from rolldown-version-stats.json:

import rolldownStats from '../../../rolldown-version-stats.json'

const buildTimeData = rolldownStats.map(stat => ({
  name: `v${stat.version}`,
  value: stat.buildTime
}))

When dashboard code changes are merged to main, the build statistics may also change (different bundle sizes, build times, etc.), so the stats need to be automatically updated to keep the visualizations accurate.

Implementation details

The workflow follows existing CI patterns and includes:

• Proper permissions (contents: write) to commit back to the main branch
• Smart change detection that only commits when rolldown-version-stats.json actually changes
• Direct push to main branch after stats collection
• Comprehensive error handling for cases where no updates are needed
• Uses maintainer's git configuration for commits

The pnpm rolldown:stats command analyzes build performance across multiple rolldown versions, generating fresh statistics that include timestamps, build times, bundle sizes, and file breakdowns.

Fixes #26.

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[Boshen]

@copilot change to change on main branch

[Copilot]

Changed the trigger to push on main branch instead of pull_request. The workflow will now run when changes are pushed to the main branch. (63469e9)

[Boshen]

@copilot replace email to my email [email protected]

[Copilot]

Replaced email with [email protected] in the git config. (63469e9)

[Boshen]

@copilot replace with my name Boshen

[Copilot]

Replaced username with "Boshen" in the git config. (63469e9)