merge: resolve v1.23.0 upstream conflicts, preserve custom git provider config

Resolved conflicts in 8 files by taking upstream refactored code:
- desktop.ts: re-export DesktopSettings from registry
- openchamberConfig.ts: simplified project setup client
- persistence.ts: registry-derived settings, add git provider hydration
- search.ts: upstream search entries + git provider entries
- useConfigStore.ts: loadDesktopSettings() path
- settings-helpers.js: add gitProviderId/gitModelId/gitProviders sanitization
- DOCUMENTATION.md: upstream walkthrough docs
- vite.config.ts: upstream SW glob patterns

Custom fork additions preserved:
- gitProviderId, gitModelId, gitProviders fields in settings registry
- Git provider domain store hydration in persistence.ts
- Git provider search entries in search.ts
- Git provider sanitization in settings-helpers.js

README.md

@@ -156,7 +156,7 @@ Special thanks to:
 
 - [OpenCode](https://opencode.ai) for the API and open-source architecture OpenChamber builds on
 - [Pierre](https://pierrejs-docs.vercel.app/) for the diff viewer and syntax highlighting
-- [Ghostty-web](https://github.com/coder/ghostty-web) for its Ghostty web renderer
+- The [T3 Code](https://github.com/pingdotgg/t3code) team for their browser adapter for [libghostty-vt](https://github.com/ghostty-org/ghostty), which our terminal is built on
 - [Yulia Ivashko](https://github.com/yulia-ivashko), who built the firework celebration that plays on every successful push
 - Everyone who contributed code, reported bugs, or shared ideas