extend build-info bake to name + tagline + repository

User asked for the rest of the pubspec-derived strings to share the
same path the version went down. gen-build-info now also writes
`clideName`, `clideTagline`, `clideRepository` to
lib/src/build_info.g.dart from pubspec.yaml. Added a `tagline:`
field to pubspec for the short user-facing line (the welcome
subtitle, future web meta) — pubspec stays the single source of
truth for every name/tagline/version/repository string the app
shows.

Consumers swept:
* welcome banner ('clide' / 'IDE for Claude Code CLI') and status
  line version label read from the constants.
* app.dart WidgetsApp title + project-switcher label use clideName.
* clide_column_hat uses clideName for the empty-projects fallback.

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

lib/widgets/src/clide_column_hat.dart

@@ -1,5 +1,6 @@
 import 'dart:io' show Platform;
 
+import 'package:clide/clide.dart' show clideName;
 import 'package:clide/kernel/src/theme/controller.dart';
 import 'package:clide/kernel/src/theme/tokens.dart';
 import 'package:clide/kernel/src/window_controls.dart';
@@ -71,7 +72,7 @@ class _CenterContent extends StatelessWidget {
     final parts = <String>[];
     if (project != null) parts.add(project!);
     if (branch != null) parts.add(branch!);
-    final label = parts.isEmpty ? 'clide' : parts.join(' > ');
+    final label = parts.isEmpty ? clideName : parts.join(' > ');
     return Center(
       child: ClideText(label, fontSize: 12, color: tokens.globalTextMuted, fontFamily: clideMonoFamily),
     );