update CLAUDE.md and reserve decision/ticket/claude-control slots

CLAUDE.md gains a "Decision discipline" guardrail pointing at
decisions/<domain>.md, rewrites every inline ADR link to the new
anchor-link style (ADR 0001 → D-001, etc.), collapses the bottom
"Open questions" section to a one-line pointer, and updates the
parent-project note to reference decisions/architecture.md instead
of the deleted docs/ADRs/.

Three extension slots are reserved with id-only stubs, registered
alongside the existing 21 built-ins in main.dart:
  - builtin.decisions — future sidebar for D/Q/R records
  - builtin.tickets — future sidebar + kanban workspace
  - builtin.claude-control — future .claude/ first-class surface
    (Settings / Skills / Agents / Hooks / MCP). Distinct from the
    existing builtin.claude PTY-pane stub.

`flutter analyze` clean; builtin + a11y test suites still pass.

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

app/lib/main.dart

@@ -1,6 +1,8 @@
 import 'package:clide_app/app.dart';
 import 'package:clide_app/builtin/canvas/canvas.dart';
 import 'package:clide_app/builtin/claude/claude.dart';
+import 'package:clide_app/builtin/claude_control/claude_control.dart';
+import 'package:clide_app/builtin/decisions/decisions.dart';
 import 'package:clide_app/builtin/default_layout/default_layout.dart';
 import 'package:clide_app/builtin/diff/diff.dart';
 import 'package:clide_app/builtin/editor/editor.dart';
@@ -18,6 +20,7 @@ import 'package:clide_app/builtin/problems/problems.dart';
 import 'package:clide_app/builtin/settings_ui/settings_ui.dart';
 import 'package:clide_app/builtin/terminal/terminal.dart';
 import 'package:clide_app/builtin/theme_picker/theme_picker.dart';
+import 'package:clide_app/builtin/tickets/tickets.dart';
 import 'package:clide_app/builtin/todos/todos.dart';
 import 'package:clide_app/builtin/welcome/welcome.dart';
 import 'dart:io' show Directory, Platform;
@@ -75,7 +78,10 @@ Future<void> main() async {
     ..register(GraphExtension())
     ..register(SettingsUiExtension())
     ..register(ExtensionsUiExtension())
-    ..register(KeybindingsUiExtension());
+    ..register(KeybindingsUiExtension())
+    ..register(DecisionsExtension())
+    ..register(TicketsExtension())
+    ..register(ClaudeControlExtension());
 
   await services.extensions.activateAll();