refactor(i18n): route planning-pane labels through the catalog (T-467)

Migrate the user-facing strings in builtin.tickets, builtin.pql,
builtin.decisions, and builtin.problems (list/detail views, section headers,
filters, empty/loading/error states, type chips) to ClideSettings.i18n; extend
each extension's catalog. The detail/links tabs that had a bare title now wire
titleKey + i18nNamespace so the tab title resolves too. Context threaded into
the static label helpers. No en_US behaviour change (D-21).

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

lib/builtin/pql/src/backlinks_view.dart

@@ -42,10 +42,22 @@ class _BacklinksViewState extends State<BacklinksView> {
       builder: (context, _) {
         final tokens = ClideSettings.theme.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 Padding(
+            padding: const EdgeInsets.all(12),
+            child: ClideText(
+              ClideSettings.i18n.string(context, 'backlinks.empty', namespace: 'builtin.pql', placeholder: 'Open a file to see its links.'),
+              muted: true,
+            ),
+          );
         }
         return Semantics(
-          label: 'backlinks for ${c.activePath}',
+          label: ClideSettings.i18n.interpolated(
+            context,
+            'backlinks.semantics',
+            namespace: 'builtin.pql',
+            placeholder: 'backlinks for {path}',
+            replacers: [I18nReplacer(from: '{path}', replace: c.activePath!)],
+          ),
           container: true,
           explicitChildNodes: true,
           child: SingleChildScrollView(
@@ -63,9 +75,21 @@ class _BacklinksViewState extends State<BacklinksView> {
                     padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 4),
                     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)
+                  Padding(
+                    padding: const EdgeInsets.all(12),
+                    child: ClideText(ClideSettings.i18n.string(context, 'backlinks.loading', namespace: 'builtin.pql', placeholder: 'Loading…'), muted: true),
+                  ),
+                _LinkGroup(
+                  label: ClideSettings.i18n.string(context, 'group.backlinks', namespace: 'builtin.pql', placeholder: 'Backlinks'),
+                  links: c.backlinks,
+                  pathKey: 'source',
+                ),
+                _LinkGroup(
+                  label: ClideSettings.i18n.string(context, 'group.outlinks', namespace: 'builtin.pql', placeholder: 'Outlinks'),
+                  links: c.outlinks,
+                  pathKey: 'target',
+                ),
               ],
             ),
           ),
@@ -90,12 +114,29 @@ class _LinkGroup extends StatelessWidget {
       children: [
         Padding(
           padding: const EdgeInsets.only(left: 12, right: 8, top: 8, bottom: 2),
-          child: ClideText('$label (${links.length})', fontSize: clideFontCaption, muted: true),
+          child: ClideText(
+            ClideSettings.i18n.interpolated(
+              context,
+              'group.label',
+              namespace: 'builtin.pql',
+              placeholder: '{label} ({count})',
+              replacers: [
+                I18nReplacer(from: '{label}', replace: label),
+                I18nReplacer(from: '{count}', replace: '${links.length}'),
+              ],
+            ),
+            fontSize: clideFontCaption,
+            muted: true,
+          ),
         ),
         if (links.isEmpty)
-          const Padding(
-            padding: EdgeInsets.symmetric(horizontal: 20, vertical: 2),
-            child: ClideText('None', fontSize: clideFontCaption, muted: true),
+          Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 20, vertical: 2),
+            child: ClideText(
+              ClideSettings.i18n.string(context, 'group.none', namespace: 'builtin.pql', placeholder: 'None'),
+              fontSize: clideFontCaption,
+              muted: true,
+            ),
           ),
         for (final link in links) _LinkRow(link: link, pathKey: pathKey),
       ],

lib/builtin/pql/src/extension.dart

@@ -21,6 +21,8 @@ class PqlExtension extends ClideExtension {
       id: 'pql.backlinks',
       slot: Slots.contextPanel,
       title: 'Links',
+      titleKey: 'tab.links.title',
+      i18nNamespace: id,
       icon: PhosphorIcons.byName('link'),
       priority: -80,
       build: (_) => const BacklinksView(),

lib/builtin/pql/src/pql_search_body.dart

@@ -104,7 +104,7 @@ class _PqlSearchBodyState extends State<PqlSearchBody> {
             if (widget.mode == PqlPaneMode.markdown)
               ClideFilterBox(
                 address: 'search.pql.markdown',
-                hint: 'Filter markdown…',
+                hint: ClideSettings.i18n.string(context, 'filter.markdown.hint', namespace: 'builtin.pql', placeholder: 'Filter markdown…'),
                 onChanged: (v) => unawaited(c.loadMarkdownFiles(glob: v.isEmpty ? null : '**/*$v*.md')),
               )
             else
@@ -118,9 +118,19 @@ class _PqlSearchBodyState extends State<PqlSearchBody> {
                 padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 4),
                 child: ClideText(c.error!, color: tokens.statusError, fontSize: clideFontCaption, maxLines: 3),
               ),
-            if (c.loading && c.results.isEmpty) const Padding(padding: EdgeInsets.all(12), child: ClideText('Loading…', muted: true)),
+            if (c.loading && c.results.isEmpty)
+              Padding(
+                padding: const EdgeInsets.all(12),
+                child: ClideText(ClideSettings.i18n.string(context, 'loading', namespace: 'builtin.pql', placeholder: 'Loading…'), muted: true),
+              ),
             if (!c.loading && c.results.isEmpty && c.error == null && widget.mode == PqlPaneMode.markdown)
-              const Padding(padding: EdgeInsets.all(12), child: ClideText('No markdown files found.', muted: true)),
+              Padding(
+                padding: const EdgeInsets.all(12),
+                child: ClideText(
+                  ClideSettings.i18n.string(context, 'empty.markdown', namespace: 'builtin.pql', placeholder: 'No markdown files found.'),
+                  muted: true,
+                ),
+              ),
             Expanded(
               child: SingleChildScrollView(
                 padding: const EdgeInsets.symmetric(vertical: 4),
@@ -160,7 +170,9 @@ class _PqlSearchInput extends StatelessWidget {
   Widget build(BuildContext context) {
     return ClideFilterBox(
       address: address,
-      hint: dsl ? 'PQL query…' : 'Search vault…',
+      hint: dsl
+          ? ClideSettings.i18n.string(context, 'search.query.hint', namespace: 'builtin.pql', placeholder: 'PQL query…')
+          : ClideSettings.i18n.string(context, 'search.vault.hint', namespace: 'builtin.pql', placeholder: 'Search vault…'),
       debounce: dsl ? Duration.zero : const Duration(milliseconds: 300),
       onChanged: dsl ? (_) {} : (v) => unawaited(controller.search(v)),
       onSubmitted: dsl ? (v) => unawaited(controller.runQuery(v)) : (v) => unawaited(controller.search(v)),