chore: adopt Dart 3.9 toolchain — honest floor + tall-style reformat (T-353)

Raise the declared minimums in pubspec.yaml to what our deps already
require: Flutter >=3.35.0 / Dart >=3.9.0 (was 3.19.0 / 3.5.0). alchemist
0.12 needs Flutter 3.32; Dart 3.9 first ships in Flutter 3.35, so 3.35 is
the binding floor. Pin the exact build toolchain in .fvmrc (Flutter
3.44.1).

Moving to the Dart 3.9 language level switches `dart format` to the new
"tall" style and enables two new lints. This commit is the resulting
mechanical churn, isolated from any behaviour change:
  - whole-tree `dart format` reformat (tall style)
  - `dart fix` for unnecessary_underscores + use_null_aware_elements

No runtime behaviour change; `make test` green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/builtin/pql/src/backlinks_view.dart

@@ -42,13 +42,7 @@ class _BacklinksViewState extends State<BacklinksView> {
       builder: (context, _) {
         final tokens = ClideTheme.of(context).surface;
         if (c.activePath == null) {
-          return const Padding(
-            padding: EdgeInsets.all(12),
-            child: ClideText(
-              'Open a file to see its links.',
-              muted: true,
-            ),
-          );
+          return const Padding(padding: EdgeInsets.all(12), child: ClideText('Open a file to see its links.', muted: true));
         }
         return Semantics(
           label: 'backlinks for ${c.activePath}',
@@ -62,35 +56,16 @@ class _BacklinksViewState extends State<BacklinksView> {
               children: [
                 Padding(
                   padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 4),
-                  child: ClideText(
-                    c.activePath!.split('/').last,
-                    color: tokens.globalForeground,
-                  ),
+                  child: ClideText(c.activePath!.split('/').last, color: tokens.globalForeground),
                 ),
                 if (c.error != null)
                   Padding(
                     padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 4),
-                    child: ClideText(
-                      c.error!,
-                      color: tokens.statusError,
-                      fontSize: clideFontCaption,
-                    ),
+                    child: ClideText(c.error!, color: tokens.statusError, fontSize: clideFontCaption),
                   ),
-                if (c.loading)
-                  const Padding(
-                    padding: EdgeInsets.all(12),
-                    child: ClideText('Loading…', muted: true),
-                  ),
-                _LinkGroup(
-                  label: 'Backlinks',
-                  links: c.backlinks,
-                  pathKey: 'source',
-                ),
-                _LinkGroup(
-                  label: 'Outlinks',
-                  links: c.outlinks,
-                  pathKey: 'target',
-                ),
+                if (c.loading) const Padding(padding: EdgeInsets.all(12), child: ClideText('Loading…', muted: true)),
+                _LinkGroup(label: 'Backlinks', links: c.backlinks, pathKey: 'source'),
+                _LinkGroup(label: 'Outlinks', links: c.outlinks, pathKey: 'target'),
               ],
             ),
           ),
@@ -101,11 +76,7 @@ class _BacklinksViewState extends State<BacklinksView> {
 }
 
 class _LinkGroup extends StatelessWidget {
-  const _LinkGroup({
-    required this.label,
-    required this.links,
-    required this.pathKey,
-  });
+  const _LinkGroup({required this.label, required this.links, required this.pathKey});
 
   final String label;
   final List<Map<String, Object?>> links;
@@ -119,11 +90,7 @@ class _LinkGroup extends StatelessWidget {
       children: [
         Padding(
           padding: const EdgeInsets.only(left: 12, right: 8, top: 8, bottom: 2),
-          child: ClideText(
-            '$label (${links.length})',
-            fontSize: clideFontCaption,
-            muted: true,
-          ),
+          child: ClideText('$label (${links.length})', fontSize: clideFontCaption, muted: true),
         ),
         if (links.isEmpty)
           const Padding(

lib/builtin/pql/src/extension.dart

@@ -17,13 +17,13 @@ class PqlExtension extends ClideExtension {
   // tab (T-201); this extension keeps only the Backlinks context panel.
   @override
   List<ContributionPoint> get contributions => [
-        TabContribution(
-          id: 'pql.backlinks',
-          slot: Slots.contextPanel,
-          title: 'Links',
-          icon: PhosphorIcons.byName('link'),
-          priority: -80,
-          build: (_) => const BacklinksView(),
-        ),
-      ];
+    TabContribution(
+      id: 'pql.backlinks',
+      slot: Slots.contextPanel,
+      title: 'Links',
+      icon: PhosphorIcons.byName('link'),
+      priority: -80,
+      build: (_) => const BacklinksView(),
+    ),
+  ];
 }

lib/builtin/pql/src/pql_controller.dart

@@ -71,10 +71,7 @@ class PqlController extends ChangeNotifier {
     _error = null;
     notifyListeners();
 
-    final r = await ipc.request('pql.search', args: {
-      'terms': terms,
-      'limit': 50,
-    });
+    final r = await ipc.request('pql.search', args: {'terms': terms, 'limit': 50});
 
     _loading = false;
     if (!r.ok) {
@@ -91,10 +88,7 @@ class PqlController extends ChangeNotifier {
     _loading = true;
     notifyListeners();
 
-    final r = await ipc.request('pql.files', args: {
-      'glob': glob ?? '**/*.md',
-      'limit': 200,
-    });
+    final r = await ipc.request('pql.files', args: {'glob': glob ?? '**/*.md', 'limit': 200});
 
     _loading = false;
     if (!r.ok) {
@@ -113,10 +107,7 @@ class PqlController extends ChangeNotifier {
     _error = null;
     notifyListeners();
 
-    final r = await ipc.request('pql.query', args: {
-      'query': dsl,
-      'limit': 200,
-    });
+    final r = await ipc.request('pql.query', args: {'query': dsl, 'limit': 200});
 
     _loading = false;
     if (!r.ok) {

lib/builtin/pql/src/pql_search_body.dart

@@ -59,8 +59,8 @@ class _PqlSearchBodyState extends State<PqlSearchBody> {
         .on<DaemonEvent>()
         .where((e) => e.subsystem == 'files' && e.kind == 'files.changed' && (e.data['path'] as String? ?? '').endsWith('.md'))
         .listen((_) {
-      if (widget.controller.view == PqlView.markdown) unawaited(widget.controller.loadMarkdownFiles());
-    });
+          if (widget.controller.view == PqlView.markdown) unawaited(widget.controller.loadMarkdownFiles());
+        });
   }
 
   @override
@@ -187,10 +187,7 @@ class _SearchResultRow extends StatelessWidget {
         },
         builder: (context, hovered, _) => Container(
           padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 6),
-          decoration: BoxDecoration(
-            color: hovered ? tokens.sidebarItemHover : null,
-            borderRadius: BorderRadius.circular(4),
-          ),
+          decoration: BoxDecoration(color: hovered ? tokens.sidebarItemHover : null, borderRadius: BorderRadius.circular(4)),
           child: Column(
             crossAxisAlignment: CrossAxisAlignment.start,
             mainAxisSize: MainAxisSize.min,
@@ -259,13 +256,7 @@ class _FileRow extends StatelessWidget {
             borderRadius: BorderRadius.circular(4),
             border: focused ? Border.all(color: tokens.globalFocus, width: 1) : null,
           ),
-          child: ClideText(
-            path,
-            maxLines: 1,
-            overflow: TextOverflow.ellipsis,
-            fontSize: clideFontCaption,
-            color: tokens.sidebarForeground,
-          ),
+          child: ClideText(path, maxLines: 1, overflow: TextOverflow.ellipsis, fontSize: clideFontCaption, color: tokens.sidebarForeground),
         ),
       ),
     );