feat(ollama): use nexus-core/models as the model store on Windows too

Windows pulled into %USERPROFILE%\.ollama while ncp and doctor looked in
nexus-core\models. The installer now sets OLLAMA_MODELS for its pulls and moves
an existing default store across first (instant on the same volume, no
refetch), and ollama_manager sets OLLAMA_MODELS on every platform. The env block
was duplicated in two methods, which is why the carve-out existed twice; folded
into _serve_env().

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

install-windows.ps1

@@ -218,6 +218,31 @@ if ($LASTEXITCODE -ne 0 -or -not $ChatModel -or -not $MemModel) {
     Write-Fail "Could not read the default models from synapse\nexus_config.py - the venv install is broken"
 }
 
+# Models live in the project's own store on both platforms, so `ncp models list`
+# and a NexusOS-spawned `ollama serve` agree on where they are. Without this the
+# installer pulled into %USERPROFILE%\.ollama and NexusOS looked somewhere else.
+Write-Step "Pointing Ollama at the project model store"
+$ModelStore = Join-Path $RepoRoot "models"
+New-Item -ItemType Directory -Path $ModelStore -Force | Out-Null
+# An existing install has GBs already downloaded in the default store. Move it
+# rather than make the user fetch it again; on the same volume this is instant.
+$LegacyStore = Join-Path $env:USERPROFILE ".ollama\models"
+if ((Test-Path (Join-Path $LegacyStore "blobs")) -and
+    -not (Test-Path (Join-Path $ModelStore "blobs"))) {
+    Write-Host "    Moving models from $LegacyStore (no re-download)..." -ForegroundColor DarkGray
+    try {
+        foreach ($sub in @("blobs", "manifests")) {
+            $src = Join-Path $LegacyStore $sub
+            if (Test-Path $src) { Move-Item -Path $src -Destination (Join-Path $ModelStore $sub) -Force }
+        }
+        Write-OK "Existing models moved into $ModelStore"
+    } catch {
+        Write-Warn "Could not move the old model store - the pull below will refetch."
+    }
+}
+$env:OLLAMA_MODELS = $ModelStore
+Write-OK "Model store: $ModelStore"
+
 Write-Step "Pulling models ($ChatModel for chat, $MemModel for memory)"
 Write-Host "    Downloads a few GB; press Ctrl+C to skip and pull them later from the Models tab." -ForegroundColor DarkGray
 # No pipe: 'ollama pull' draws a progress bar with cursor control, and piping it