feat(projects): support multiple repositories (#4671)

## Summary
- adopt the finalized NIP-MP project model so one project can enumerate
and switch between multiple NIP-34 repositories
- add project and repository navigation, activity summaries,
existing-repository attachment, and repository access-channel management
- preserve privacy-safe activation provenance for agent-authored
patches, pull requests, issues, and associated commits

## Test plan
- [x] Run desktop typecheck and unit tests
- [x] Run focused NIP-MP, repository access, and provenance tests
- [x] Run Rust formatting and desktop lint checks
- [x] Run the complete pre-push suite after merging current `main`
- [ ] Manually verify project creation, repository attachment,
switching, and access repair on staging
- [ ] Manually verify public-channel and private-agent origin labels on
newly created Git activity

Related: [#4695](https://github.com/block/buzz/pull/4695)

---------

Signed-off-by: Thomas Petersen <thomasp@squareup.com>
Signed-off-by: Will Pfleger <pfleger.will@gmail.com>
Co-authored-by: npub1mn7jgtj4w2pd0g0zeuhxsa6jy6p0rewxz4kujt98my82ahfmp72sxjexk7 <dcfd242e557282d7a1e2cf2e6877522682f1e5c6156dc92ca7d90eaedd3b0f95@buzz.block.builderlab.xyz>
Co-authored-by: Will Pfleger <pfleger.will@gmail.com>

desktop/vite.config.ts

@@ -3,7 +3,6 @@ import { defineConfig } from "vite";
 import react from "@vitejs/plugin-react";
 import { tanstackRouter } from "@tanstack/router-plugin/vite";
 
-// @ts-expect-error process is a nodejs global
 const host = process.env.TAURI_DEV_HOST;
 
 // https://vite.dev/config/