refactor(cli): replace slash command whitelist with capability-based filtering (Phase 1) (#3283)

* refactor(cli): replace slash command whitelist with capability-based filtering (Phase 1)

## Summary

Replace the hardcoded ALLOWED_BUILTIN_COMMANDS_NON_INTERACTIVE whitelist with a
unified, capability-based command metadata model. This is Phase 1 of the slash
command architecture refactor described in docs/design/slash-command/.

## Key changes

### New types (types.ts)
- Add ExecutionMode ('interactive' | 'non_interactive' | 'acp')
- Add CommandSource ('builtin-command' | 'bundled-skill' | 'skill-dir-command' |
  'plugin-command' | 'mcp-prompt')
- Add CommandType ('prompt' | 'local' | 'local-jsx')
- Extend SlashCommand interface with: source, sourceLabel, commandType,
  supportedModes, userInvocable, modelInvocable, argumentHint, whenToUse,
  examples (all optional, backward-compatible)

### New module (commandUtils.ts + commandUtils.test.ts)
- getEffectiveSupportedModes(): 3-priority inference
  (explicit supportedModes > commandType > CommandKind fallback)
- filterCommandsForMode(): replaces filterCommandsForNonInteractive()
- 18 unit tests

### Whitelist removal (nonInteractiveCliCommands.ts)
- Remove ALLOWED_BUILTIN_COMMANDS_NON_INTERACTIVE constant
- Remove filterCommandsForNonInteractive() function
- Replace with CommandService.getCommandsForMode(mode)

### CommandService enhancements (CommandService.ts)
- Add getCommandsForMode(mode: ExecutionMode): filters by mode, excludes hidden
- Add getModelInvocableCommands(): reserved for Phase 3 model tool-call use

### Built-in command annotations (41 files)
Annotate every built-in command with commandType:
- commandType='local' + supportedModes all-modes: btw, bug, compress, context,
  init, summary (replaces the 6-command whitelist)
- commandType='local' interactive-only: export, memory, plan, insight
- commandType='local-jsx' interactive-only: all remaining ~31 commands

### Loader metadata injection (4 files)
Each loader stamps source/sourceLabel/commandType/modelInvocable on every
command it emits:
- BuiltinCommandLoader: source='builtin-command', modelInvocable=false
- BundledSkillLoader: source='bundled-skill', commandType='prompt',
  modelInvocable=true
- command-factory (FileCommandLoader): source per extension/user origin,
  commandType='prompt', modelInvocable=!extensionName
- McpPromptLoader: source='mcp-prompt', commandType='prompt', modelInvocable=true

### Bug fix
MCP_PROMPT commands were incorrectly excluded from non-interactive/ACP modes by
the old whitelist logic. commandType='prompt' now correctly allows them in all
modes.

### Session.ts / nonInteractiveHelpers.ts
- ACP session calls getAvailableCommands with explicit 'acp' mode
- Remove allowedBuiltinCommandNames parameter from buildSystemMessage() —
  capability filtering is now self-contained in CommandService

* fix test ci

* fix memory command

* fix: pass 'non_interactive' mode explicitly to getAvailableCommands

- Fix critical bug in nonInteractiveHelpers.ts: loadSlashCommandNames was
  calling getAvailableCommands without specifying mode, causing it to default
  to 'acp' instead of 'non_interactive'. Commands with supportedModes that
  include 'non_interactive' but not 'acp' would be silently excluded.
- Apply the same fix in systemController.ts for the same reason.
- Update test mock to delegate filtering to production filterCommandsForMode()
  instead of duplicating the logic inline, preventing divergence.

Fixes review comments by wenshao and tanzhenxin on PR #3283.

* fix: resolve TypeScript type error in nonInteractiveHelpers.test.ts

* fix test ci

packages/cli/src/nonInteractiveCli.test.ts

@@ -26,7 +26,8 @@ import type { Part } from '@google/genai';
 import { runNonInteractive } from './nonInteractiveCli.js';
 import { vi, type Mock, type MockInstance } from 'vitest';
 import type { LoadedSettings } from './config/settings.js';
-import { CommandKind } from './ui/commands/types.js';
+import { CommandKind, type ExecutionMode } from './ui/commands/types.js';
+import { filterCommandsForMode } from './services/commandUtils.js';
 
 // Mock core modules
 vi.mock('./ui/hooks/atCommandProcessor.js');
@@ -54,6 +55,7 @@ vi.mock('@qwen-code/qwen-code-core', async (importOriginal) => {
 });
 
 const mockGetCommands = vi.hoisted(() => vi.fn());
+const mockGetCommandsForMode = vi.hoisted(() => vi.fn());
 const mockCommandServiceCreate = vi.hoisted(() => vi.fn());
 vi.mock('./services/CommandService.js', () => ({
   CommandService: {
@@ -79,8 +81,12 @@ describe('runNonInteractive', () => {
   beforeEach(async () => {
     mockCoreExecuteToolCall = vi.mocked(executeToolCall);
     mockShutdownTelemetry = vi.mocked(shutdownTelemetry);
+    mockGetCommandsForMode.mockImplementation((mode: ExecutionMode) =>
+      filterCommandsForMode(mockGetCommands(), mode),
+    );
     mockCommandServiceCreate.mockResolvedValue({
       getCommands: mockGetCommands,
+      getCommandsForMode: mockGetCommandsForMode,
     });
 
     processStdoutSpy = vi
@@ -976,7 +982,7 @@ describe('runNonInteractive', () => {
 
     // Should write error message through adapter to stdout (TEXT mode goes through JsonOutputAdapter)
     expect(processStderrSpy).toHaveBeenCalledWith(
-      'The command "/help" is not supported in non-interactive mode.\n',
+      'The command "/help" is not supported in this mode.\n',
     );
   });