v1.5.5: terminal zoom, font fallback, copy feedback

- Ctrl+wheel/Ctrl±/Ctrl+0 font zoom (6-28), persisted in settings.json
- Font fallback: Cascadia Mono → Consolas → Courier New (per platform)
- Visual "Copied!" flash in status bar on copy
- Closes audit items #27 (copy feedback) and #29 (font fallback)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

gui/tabs/terminal_tab.py

@@ -27,6 +27,8 @@ class TerminalTab(ctk.CTkFrame):
             self,
             send_callback=self._send_to_shell,
             resize_callback=self._on_resize,
+            font_size=store.get_terminal_font_size(),
+            on_font_size_changed=self._on_font_size_changed,
         )
         self._terminal.pack(fill="both", expand=True, padx=5, pady=5)
         self._terminal.set_status(t("term_disconnected"), "#888888")
@@ -145,3 +147,6 @@ class TerminalTab(ctk.CTkFrame):
         session = self._session  # local ref for thread safety
         if session and session.connected:
             session.resize(cols, rows)
+
+    def _on_font_size_changed(self, size: int):
+        self.store.set_terminal_font_size(size)