Add repository_customizations table and routes

ENVIRONMENT.md

@@ -98,6 +98,7 @@ Manage shared web env var additions and rotations with `pnpm web:env set <VARIAB
 - `GITHUB_LITE_APP_CLIENT_ID` - OAuth Client ID for the lite GitHub App install/login flow. [PUBLIC]
 - `GITHUB_MULTIPLE_INSTALLATION_ORGANIZATION_IDS` - Comma-separated Kilo organization UUIDs allowed to connect multiple GitHub App installations. Unset or empty disables multiple installations for all organizations. [SERVER]
 - `GITHUB_CONNECTION_MANAGEMENT_ENABLED` - Set to exact `true` to admit new existing-installation connection management and local disconnect. Unset or any other value keeps new management admission disabled without changing incumbent GitHub integration workflows. [SERVER]
+- `PER_REPO_SETTINGS` - Set to exactly `true` to reveal the Repository Customizations UI (per-installation default AI model / PR review mode, plus per-repository overrides) on the GitHub integration settings pages, for both personal accounts and organizations. Defaults to disabled so the feature can ship dark. [SERVER]
 - `GITHUB_ADMIN_STATS_TOKEN` - Token for admin GitHub API stats lookups; used in `apps/web/src/scripts/backfill-pr-author-github-ids.ts`. `[SECRET]`
 - `GITHUB_CLI_PAT` - GitHub personal access token for `gh` CLI operations inside contractors; used in `services/gastown/container/src/process-manager.ts`. `[SECRET]`
 - `GITHUB_TOKEN` - Generic GitHub token for API calls used as fallback when `GIT_TOKEN` or `GITHUB_CLI_PAT` is absent; used in `services/gastown/container/src/process-manager.ts`. `[SECRET]`

apps/web/src/components/integrations/GitHubIntegrationDetails.tsx

@@ -25,6 +25,7 @@ import { useModelSelectorList } from '@/app/api/openrouter/hooks';
 import { buildGitHubInstallState } from './github-install-state';
 import { useConfirm } from '@/components/ui/confirm';
 import { OrganizationGitHubInstallations } from './OrganizationGitHubInstallations';
+import { InstallationCustomizations } from './GitHubRepositoryCustomizationsPreview';
 
 type GitHubIntegrationDetailsProps = {
   organizationId?: string;
@@ -40,6 +41,10 @@ type GitHubIntegrationDetailsProps = {
   existingPendingOrg?: string;
   appReturnPath?: string;
   onInstallationDetected?: () => void;
+  /** Reveals the Repository Customizations UI (default AI model / PR review
+   *  mode plus per-repository overrides) behind the PER_REPO_SETTINGS flag.
+   *  Computed server-side and threaded down since this is a client component. */
+  perRepoSettingsEnabled?: boolean;
 };
 
 /**
@@ -233,7 +238,10 @@ export function GitHubIntegrationDetails(props: GitHubIntegrationDetailsProps) {
       <GitHubIntegrationOutcomeToasts {...props} />
       {props.organizationId && !props.appReturnPath ? (
         <div className="space-y-6">
-          <OrganizationGitHubInstallations organizationId={props.organizationId} />
+          <OrganizationGitHubInstallations
+            organizationId={props.organizationId}
+            perRepoSettingsEnabled={props.perRepoSettingsEnabled}
+          />
           <Card>
             <CardHeader>
               <div className="space-y-1.5">
@@ -274,6 +282,7 @@ function GitHubIntegrationDetailsContent({
   pendingApproval,
   appReturnPath,
   onInstallationDetected,
+  perRepoSettingsEnabled,
 }: GitHubIntegrationDetailsProps) {
   const trpc = useTRPC();
   const queryClient = useQueryClient();
@@ -899,17 +908,19 @@ function GitHubIntegrationDetailsContent({
               </div>
 
               {/* Model Selection */}
-              <div className="space-y-3 rounded-lg border p-4">
-                <ModelCombobox
-                  label="AI Model"
-                  helperText="Select the AI model to use when responding to GitHub bot mentions"
-                  models={modelOptions}
-                  value={selectedModel}
-                  onValueChange={handleModelChange}
-                  isLoading={isLoadingModels}
-                  placeholder="Select a model"
-                />
-              </div>
+              {!perRepoSettingsEnabled && (
+                <div className="space-y-3 rounded-lg border p-4">
+                  <ModelCombobox
+                    label="AI Model"
+                    helperText="Select the AI model to use when responding to GitHub bot mentions"
+                    models={modelOptions}
+                    value={selectedModel}
+                    onValueChange={handleModelChange}
+                    isLoading={isLoadingModels}
+                    placeholder="Select a model"
+                  />
+                </div>
+              )}
 
               {/* Actions */}
               <div className="flex flex-wrap gap-3">
@@ -1000,6 +1011,15 @@ function GitHubIntegrationDetailsContent({
         </CardContent>
       </Card>
 
+      {isInstalled && installation && !isPendingApproval && perRepoSettingsEnabled && (
+        <InstallationCustomizations
+          integrationId={installation.id}
+          organizationId={organizationId}
+          models={modelOptions}
+          initiallyOpen={false}
+        />
+      )}
+
       {!organizationId ? (
         <Card id="github-identity">
           <CardHeader>