docs: fix broken anchor links and add migrate-rules to sidebar (#2203)

## Summary

Fixes four broken internal anchor links in the docs site and adds the
previously-orphaned Migration Rules page to the guide sidebar. These
surfaced during a proofreading pass over the documentation website.

## Changes

**Broken anchors** — these links resolved to the correct page but
silently failed to scroll to the target heading, because the anchor
slugs didn't match VitePress's heading slugification (which collapses
`.` and other special characters to `-`):

- `guide/github-actions-cache.md` (2 links): `/config/run#tasks` →
`/config/run#run-tasks` (heading is `## run.tasks`)
- `guide/installer-env-vars.md`: `/guide/env#custom-nodejs-mirror` →
`#custom-node-js-mirror`
- `guide/installer-env-vars.md`:
`/guide/env#nodejs-signature-verification` →
`#node-js-signature-verification`

**Navigation:**

- Added "Migration Rules" (`/guide/migrate-rules`) to the guide sidebar,
nested under "Migrate to Vite+" (matching the existing Check →
Lint/Format nesting). The page previously existed and was reachable only
through an inline link in `migrate.md`, with no sidebar entry.

Co-authored-by: Charles Wang <3612422+wan9chi@users.noreply.github.com>

Author: charpeni

docs/.vitepress/config.mts

@@ -32,7 +32,11 @@ const guideSidebar = [
     items: [
       { text: 'Getting Started', link: '/guide/' },
       { text: 'Creating a Project', link: '/guide/create' },
-      { text: 'Migrate to Vite+', link: '/guide/migrate' },
+      {
+        text: 'Migrate to Vite+',
+        link: '/guide/migrate',
+        items: [{ text: 'Migration Rules', link: '/guide/migrate-rules' }],
+      },
       { text: 'Installing Dependencies', link: '/guide/install' },
       { text: 'Environment', link: '/guide/env' },
       { text: 'Installer Environment Variables', link: '/guide/installer-env-vars' },

docs/guide/github-actions-cache.md

@@ -48,7 +48,7 @@ export default defineConfig({
 });
 ```
 
-This guide assumes each task already hits locally. If a task misses, fix its tracking config in `vite.config.ts` before adding the GitHub Actions cache steps. See [Automatic Data Tracking](/guide/automatic-data-tracking) and [`run.tasks`](/config/run#tasks).
+This guide assumes each task already hits locally. If a task misses, fix its tracking config in `vite.config.ts` before adding the GitHub Actions cache steps. See [Automatic Data Tracking](/guide/automatic-data-tracking) and [`run.tasks`](/config/run#run-tasks).
 
 Run each task twice:
 
@@ -129,7 +129,7 @@ If GitHub restores a cache but Vite Task prints a cache miss, the workflow resto
 
 ## Keep Task Tracking Stable
 
-If GitHub restores a cache but `vp run` prints a cache miss, fix the task fingerprint before changing the Actions cache key. See [Automatic Data Tracking](/guide/automatic-data-tracking) and [`run.tasks`](/config/run#tasks).
+If GitHub restores a cache but `vp run` prints a cache miss, fix the task fingerprint before changing the Actions cache key. See [Automatic Data Tracking](/guide/automatic-data-tracking) and [`run.tasks`](/config/run#run-tasks).
 
 ## Choose A Cache Key
 

docs/guide/installer-env-vars.md

@@ -81,7 +81,7 @@ These variables configure the installed Vite+ CLI. `VP_HOME` (above) also applie
 
 - **Purpose**: Node.js distribution mirror URL
 - **Default**: `https://nodejs.org/dist`
-- **Details**: [Custom Node.js Mirror](/guide/env#custom-nodejs-mirror)
+- **Details**: [Custom Node.js Mirror](/guide/env#custom-node-js-mirror)
 
 ### `VP_NODE_VERSION`
 
@@ -98,7 +98,7 @@ These variables configure the installed Vite+ CLI. `VP_HOME` (above) also applie
 - **Purpose**: Skip PGP signature verification of Node.js downloads
 - **Values**: Any non-empty value
 - **Default**: None (verification enabled)
-- **Details**: [Node.js Signature Verification](/guide/env#nodejs-signature-verification)
+- **Details**: [Node.js Signature Verification](/guide/env#node-js-signature-verification)
 
 ### `VP_SHELL`