fix(@angular/build): keep dev-server Vite cache worktree-local

[clydin]

When running within a Git worktree, the persistent build cache is shared across worktrees by resolving relative to the common Git directory (main repository root). While this works for location-agnostic compilation caches (such as ng build's SourceFileCache), it breaks ng serve when server-side rendering (SSR) is enabled.

In SSR mode, Vite prebundles dependencies into deps_ssr/. Any external or unbundled dependencies inside those prebundles contain bare imports (e.g., firebase-admin/data-connect). Because Node.js resolves bare imports relative to the prebundled file's location, placing cacheDir under the main repository root causes Node.js to resolve imports against the main repository's node_modules instead of the worktree's node_modules, resulting in Cannot find module errors and HTTP 500 responses.

To resolve this, NormalizedCachedOptions now exposes localBasePath and localPath which always resolve relative to the active workspace root. The dev-server's Vite configuration now uses localPath for cacheDir, ensuring prebundles remain within the worktree hierarchy where Node.js can resolve the worktree's dependencies. Additionally, cache purging and watcher ignore lists are updated to handle both shared and local cache paths when they diverge.

Fixes #33968

[gemini-code-assist]

Code Review

This pull request introduces workspace-local cache options (localPath and localBasePath) to support environments like Git worktrees where the cache should resolve relative to the current worktree root rather than the main repository root. It updates the build watcher, Vite dev server, cache normalization, and cache purging logic to handle these new local paths. A critical bug was identified in the cache purging logic (purge-cache.ts) where an undefined localPath could fall back to path, leading to the accidental deletion of the active local cache directory. A fix was suggested to skip purging if currentPath is not defined.