Merge branch 'main' into ci/vercel-deterministic-install

Vercel restores a cached node_modules snapshot and runs the custom
installCommand incrementally. With `npm install`, a lockfile change makes
the incremental reconcile leave gitnexus-web without a usable `tsc`
binary, so `npm run build` (`tsc -b && vite build`) fails with
`sh: line 1: tsc: command not found` (exit 127) — the failure blocking
#1705. `npm ci` ignores the restored tree and installs exactly from the
lockfile (the canonical CI/deploy install), so build tooling is always
present. `--include=dev` keeps devDependencies even if the build env sets
NODE_ENV=production. Vercel still caches the npm download store, so the
only cost is a fast relink each build.

Unblocks #1705.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

gitnexus-web/vercel.json

@@ -1,3 +1,3 @@
 {
-  "installCommand": "cd ../gitnexus-shared && npm install && npm run build && cd ../gitnexus-web && npm install"
+  "installCommand": "cd ../gitnexus-shared && npm install && npm run build && cd ../gitnexus-web && npm ci --include=dev"
 }