picker-first startup with per-project sticky override (T-115)

Boot used to auto-open app.lastProject and fall back to the CWD; new
default is the welcome screen as the project picker. Sticky-open is
opt-in: a checkbox on each recent-projects row toggles a
startupSticky flag, and clide auto-opens iff exactly one row has it.
Two-or-more, or none, ⇒ picker (unambiguous user intent).

RecentProject gains the boolean (persisted in app.recentProjects);
ProjectManager exposes stickyProjectPath, openStickyOrNothing,
setStickyStartup, isStickyStartup, and preserves the flag across
reopens.

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

lib/builtin/welcome/src/welcome_view.dart

@@ -264,7 +264,13 @@ class _RecentColumn extends StatelessWidget {
             if (recents.isEmpty)
               const ClideText('No recent projects.', muted: true, fontSize: 14)
             else
-              for (final r in recents) _RecentRow(project: r, tokens: tokens, onTap: () => _openRecent(r.path)),
+              for (final r in recents)
+                _RecentRow(
+                  project: r,
+                  tokens: tokens,
+                  onTap: () => _openRecent(r.path),
+                  onToggleSticky: () => kernel.project.setStickyStartup(r.path, !r.startupSticky),
+                ),
           ],
         );
       },
@@ -279,10 +285,16 @@ class _RecentColumn extends StatelessWidget {
 }
 
 class _RecentRow extends StatelessWidget {
-  const _RecentRow({required this.project, required this.tokens, required this.onTap});
+  const _RecentRow({
+    required this.project,
+    required this.tokens,
+    required this.onTap,
+    required this.onToggleSticky,
+  });
   final RecentProject project;
   final SurfaceTokens tokens;
   final VoidCallback onTap;
+  final VoidCallback onToggleSticky;
 
   @override
   Widget build(BuildContext context) {
@@ -318,6 +330,8 @@ class _RecentRow extends StatelessWidget {
                 ],
               ),
             ),
+            _StickyToggle(sticky: project.startupSticky, tokens: tokens, onTap: onToggleSticky),
+            const SizedBox(width: 12),
             ClideText(project.timeAgo, muted: true, fontSize: 13),
           ],
         ),
@@ -326,6 +340,41 @@ class _RecentRow extends StatelessWidget {
   }
 }
 
+/// Sticky-startup checkbox shown on each recent-project row (T-115).
+/// When exactly one row is checked, clide opens that project on next
+/// launch instead of showing the picker. Tooltip explains the rule.
+class _StickyToggle extends StatelessWidget {
+  const _StickyToggle({required this.sticky, required this.tokens, required this.onTap});
+  final bool sticky;
+  final SurfaceTokens tokens;
+  final VoidCallback onTap;
+
+  @override
+  Widget build(BuildContext context) {
+    return ClideTooltip(
+      message: sticky ? 'Always open this project on launch (uncheck to restore picker)' : 'Always open this project on launch',
+      child: Semantics(
+        button: true,
+        checked: sticky,
+        label: 'always open this project on launch',
+        child: ClideTappable(
+          onTap: onTap,
+          builder: (context, hovered, _) => Container(
+            width: 18,
+            height: 18,
+            decoration: BoxDecoration(
+              color: sticky ? tokens.statusBarItemActiveBackground : null,
+              border: Border.all(color: hovered || sticky ? tokens.panelActiveBorder : tokens.globalBorder),
+              borderRadius: BorderRadius.circular(3),
+            ),
+            child: sticky ? ClideIcon(PhosphorIcons.check, size: 12, color: tokens.buttonForeground) : null,
+          ),
+        ),
+      ),
+    );
+  }
+}
+
 class _StatusLine extends StatelessWidget {
   const _StatusLine({required this.tokens, required this.kernel});
   final SurfaceTokens tokens;