Unify TUI runtime commands with gateway and harden gateway restart

src/commands/index.ts

@@ -1,5 +1,10 @@
 export { CommandRegistry } from './registry.js';
 export type { CommandContext, CommandDefinition, CommandResult, CommandServices } from './types.js';
+export {
+  executeRuntimeBackendModeCommand,
+  formatRuntimeBackendStatusLine,
+} from './runtimeBackendMode.js';
+export type { RuntimeBackendMode } from './runtimeBackendMode.js';
 export {
   createHelpCommand,
   createStatusCommand,

src/commands/runtimeBackendMode.ts

@@ -0,0 +1,94 @@
+export type RuntimeBackendMode = 'config_default' | 'force_native' | 'force_pi_embedded';
+
+export interface RuntimeBackendModeCommandContext {
+  getActiveTier: () => string;
+  getBackendMode: () => RuntimeBackendMode;
+  getConfiguredDefaultBackend: () => string;
+  getEffectiveDefaultBackend: () => string;
+  getAvailableExternalBackends: () => string[];
+  setBackendMode?: (mode: RuntimeBackendMode) => void;
+}
+
+function normalizeRuntimeInput(inputRaw: string): string {
+  let normalized = inputRaw.trim().toLowerCase();
+  // Accept subcommand-only input and accidental full command input.
+  normalized = normalized.replace(/^(?:\/)?(?:runtime|backend)\b/, '').trim();
+  normalized = normalized.replace(/^\//, '').trim();
+  return normalized;
+}
+
+export function formatRuntimeBackendStatusLine(ctx: RuntimeBackendModeCommandContext): string {
+  const availableExternal = [...ctx.getAvailableExternalBackends()].sort().join(', ') || 'none';
+  return [
+    `Flynn is running. Active model tier: ${ctx.getActiveTier()}. Backend: ${ctx.getEffectiveDefaultBackend()}`,
+    `Backend mode: ${ctx.getBackendMode()}`,
+    `Configured default: ${ctx.getConfiguredDefaultBackend()}`,
+    `Available external backends: ${availableExternal}`,
+  ].join('\n');
+}
+
+export function executeRuntimeBackendModeCommand(
+  inputRaw: string,
+  ctx: RuntimeBackendModeCommandContext,
+): string {
+  const normalized = normalizeRuntimeInput(inputRaw);
+
+  if (!normalized || normalized === 'status' || normalized === 'show') {
+    return formatRuntimeBackendStatusLine(ctx);
+  }
+
+  if (!ctx.setBackendMode) {
+    return 'Backend mode control is not available in this runtime.';
+  }
+
+  if (
+    normalized === 'activate pi'
+    || normalized === 'activate pi_embedded'
+    || normalized === 'activate pi-embedded'
+  ) {
+    ctx.setBackendMode('force_pi_embedded');
+    return [
+      'Pi embedded backend activated globally.',
+      formatRuntimeBackendStatusLine(ctx),
+    ].join('\n\n');
+  }
+
+  if (
+    normalized === 'deactivate pi'
+    || normalized === 'deactivate pi_embedded'
+    || normalized === 'deactivate pi-embedded'
+  ) {
+    ctx.setBackendMode('force_native');
+    return [
+      'Pi embedded backend deactivated globally. Native is now forced for Pi-routed turns.',
+      formatRuntimeBackendStatusLine(ctx),
+    ].join('\n\n');
+  }
+
+  if (
+    normalized === 'use config'
+    || normalized === 'reset'
+    || normalized === 'auto'
+    || normalized === 'config'
+  ) {
+    ctx.setBackendMode('config_default');
+    return [
+      'Backend mode reset to config default.',
+      formatRuntimeBackendStatusLine(ctx),
+    ].join('\n\n');
+  }
+
+  return [
+    'Usage:',
+    '/runtime status',
+    '/runtime activate pi',
+    '/runtime deactivate pi',
+    '/runtime use config',
+    '',
+    'Alias:',
+    '/backend status',
+    '/backend activate pi',
+    '/backend deactivate pi',
+    '/backend use config',
+  ].join('\n');
+}