disable portfolio tab in symbol mode

src/tui.zig

@@ -1634,10 +1634,9 @@ pub const App = struct {
     }
 
     /// Whether the given tab should be treated as disabled in
-    /// the current App context. All migrated tabs are consulted
-    /// via their framework-contract `isDisabled` hook. (Portfolio
-    /// is the only remaining unmigrated tab; it has no disabled
-    /// predicate today.)
+    /// the current App context. All tabs are consulted via their
+    /// framework-contract `isDisabled` hook (tabs without one
+    /// default to always-enabled).
     fn isDisabled(self: *App, t: Tab) bool {
         return self.appPredicate(t, "isDisabled");
     }

src/tui/portfolio_tab.zig

@@ -330,6 +330,16 @@ pub const tab = struct {
 
     pub const deactivate = framework.noopDeactivate(State);
 
+    /// Disabled only when the TUI was opened on a specific symbol
+    /// (`zfin AAPL`) with no portfolio loaded: there's nothing to show
+    /// here, so it greys out and becomes unselectable to match the
+    /// other portfolio-backed tabs (analysis, review, projections,
+    /// history). A plain `zfin` launch with no portfolio keeps the tab
+    /// enabled so it can show the welcome screen (`drawWelcomeScreen`).
+    pub fn isDisabled(app: *App) bool {
+        return app.portfolio.file == null and app.has_explicit_symbol;
+    }
+
     /// Manual refresh (r/F5): re-value the portfolio with live
     /// intraday quotes, then rebuild the summary. `r` means "give me
     /// current prices now" - it does NOT force candle work. Candle
@@ -466,11 +476,6 @@ pub const tab = struct {
         }
     }
 
-    /// Portfolio is always enabled (the tab itself; data may be
-    /// empty if no portfolio file is loaded - that's a separate
-    /// concern handled by `drawWelcomeScreen`).
-    pub const isDisabled = framework.alwaysEnabled();
-
     /// Drop UI state that referenced the previous portfolio.
     ///
     /// `account_list` holds borrowed strings into the old