build: upgrade astro 5→6 and starlight 0.37→0.38 in docs

[staging-devin-ai-integration]

Summary

Upgrades the docs/ site dependencies:

• astro from ^5.18.1 → ^6.2.1 (Astro 6, bundling Vite 7 and Zod 4)
• @astrojs/starlight from ^0.37.7 → ^0.38.4

No code changes were needed — the existing content config, custom Starlight components (ThemeProvider.astro, ThemeSelect.astro, Mermaid.astro), and the rehype plugin all work without modification.

Verified locally:

• bun run build completes successfully (all pages generated)
• bun run dev starts the dev server without errors
• Node v22.12.0 satisfies Astro 6's requirement of Node ≥ 22.12.0

Review & Testing Checklist for Human

• Verify the docs site builds and deploys correctly in CI
• Spot-check a few pages (especially ones using Mermaid diagrams) to confirm rendering is correct
• Verify custom theme components (dark/light mode toggle) still work as expected

Notes

• Only docs/package.json and docs/bun.lock were modified — no changes outside docs/
• The project already used Content Layer API, so no migration from legacy collections was needed
• bun was used exclusively as the package manager (no npm/pnpm)

Link to Devin session: https://staging.itsdev.in/sessions/179c6ca37aae48b487485c7fce260e9e
Requested by: @streamer45

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Devin Review

Status	Commit
🟢 Reviewed	d10c19e

[staging-devin-ai-integration]

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[staging-devin-ai-integration]

Devin Review found 1 potential issue.

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[staging-devin-ai-integration]

📝 Info: Major version bump (Astro 5→6) with no code changes needed

This PR bumps Astro from v5 to v6, which is a major version. However, the @astrojs/starlight@0.38.4 explicitly declares peerDependencies: { "astro": "^6.0.0" } in the lockfile, confirming this combination is designed to work together. The existing astro.config.mjs, content.config.ts, and custom components (ThemeProvider.astro, ThemeSelect.astro) all use standard Starlight/Astro APIs that appear stable across this upgrade. The astro-expressive-code@0.41.7 transitive dependency also supports astro 6 via its peer dep "astro": "^4.0.0-beta || ^5.0.0-beta || ^3.3.0 || ^6.0.0-beta". No code changes were required, which is a good sign that the upgrade path is clean for this docs site.

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[staging-devin-ai-integration]

Manual Testing Results

Ran local docs dev server (bun run dev) on the PR branch and verified rendering in the browser. Devin session

Core Rendering Tests

Test	Result
Landing page (hero, action buttons, CardGrid, asides, code blocks)	passed
Quick Start page (code blocks with syntax highlighting, GitHub alert asides)	passed
Theme toggle (dark ↔ light, verified data-theme attribute)	passed
Sidebar navigation (5 sections, cross-section navigation)	passed
Introduction page (MDX content)	passed
Architecture Overview page (markdown content)	passed

Theme Toggle Evidence

Dark (default)	Light (after toggle)

Content Pages

Quick Start (sidebar + code blocks)	Introduction

Quick Start (scrolled to code blocks)	Architecture Overview

No issues found. All pages render correctly under Astro 6.2.1 + Starlight 0.38.4.