fix(close): Edge fallback + better tryClose + honest hint

There is no JavaScript override for browser tab-close security:
``window.close()`` only succeeds on windows JS opened (Chrome --app
windows qualify; a regular browser tab does not). What we can do is
make the --app path easier to hit and the failure case more
actionable.

Three changes:

1. ``src/gui/__main__.py`` — extend browser detection. PATH lookup
   now also looks for ``msedge`` / ``microsoft-edge``; Windows install
   candidates include the Edge install path; macOS candidates include
   Edge and Chromium. Edge is Chromium-based, supports ``--app``, and
   ships on every Windows 10+ machine — so users without Chrome no
   longer fall through to the regular browser tab. When the fallback
   IS hit, print a warning to stderr explaining why Close-from-page
   will require Ctrl+W. Renamed ``_find_chrome`` to
   ``_find_app_browser`` to reflect the broader scope.

2. ``_FAREWELL_SCRIPT_TEMPLATE`` in ``components/_legacy.py`` —
   factor close attempts into a ``tryClose`` helper that runs three
   escalating tries: standard ``win.close()``, the
   ``win.open('', '_self')`` history-rewrite trick (no-op in modern
   Chrome but free), and ``win.top.close()``. Auto-close on paint AND
   the manual button now both call this helper. Skip the manual hint
   if the close eventually succeeded between the click and the 250 ms
   timeout.

3. ``quit.close_hint`` in en/es i18n packs — rewrite the message to
   tell the user honestly that this is a browser security restriction,
   tell them the Ctrl+W keystroke that works, and point them at
   ``python -m src.gui`` for the auto-closing app-mode experience.

2008 tests pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/gui/__main__.py

@@ -16,23 +16,42 @@ from pathlib import Path
 _URL = "http://localhost:8501"
 
 
-def _find_chrome() -> str | None:
+def _find_app_browser() -> str | None:
-    """Return the path to a Chrome/Chromium executable, or None."""
+    """Return the path to a Chromium-based browser that supports --app mode.
-    # Check PATH first
+
-    for name in ("chrome", "google-chrome", "google-chrome-stable", "chromium", "chromium-browser"):
+    Chrome is preferred. Edge (Chromium-based, ships on every Windows
+    10+ install) is the fallback that lets ``window.close()`` actually
+    close the tab on the Close page — without it Windows users who
+    don't have Chrome end up in a regular browser tab where the close
+    button is silently blocked by browser security.
+    """
+    # PATH first — covers Linux package installs and devs who put their
+    # preferred browser on PATH explicitly.
+    for name in (
+        "chrome", "google-chrome", "google-chrome-stable",
+        "chromium", "chromium-browser",
+        "msedge", "microsoft-edge",
+    ):
         found = shutil.which(name)
         if found:
             return found
 
-    # Windows common install locations
+    # Windows common install locations.
     if sys.platform == "win32":
         candidates = [
+            # Chrome — preferred when present.
             Path(os.environ.get("PROGRAMFILES", r"C:\Program Files"))
             / "Google" / "Chrome" / "Application" / "chrome.exe",
             Path(os.environ.get("PROGRAMFILES(X86)", r"C:\Program Files (x86)"))
             / "Google" / "Chrome" / "Application" / "chrome.exe",
             Path(os.environ.get("LOCALAPPDATA", ""))
             / "Google" / "Chrome" / "Application" / "chrome.exe",
+            # Edge — ships with Windows 10+, Chromium-based, also
+            # supports --app and the window.close() it enables.
+            Path(os.environ.get("PROGRAMFILES(X86)", r"C:\Program Files (x86)"))
+            / "Microsoft" / "Edge" / "Application" / "msedge.exe",
+            Path(os.environ.get("PROGRAMFILES", r"C:\Program Files"))
+            / "Microsoft" / "Edge" / "Application" / "msedge.exe",
         ]
         for c in candidates:
             if c.exists():
@@ -40,21 +59,40 @@ def _find_chrome() -> str | None:
 
     # macOS
     if sys.platform == "darwin":
-        mac_chrome = Path("/Applications/Google Chrome.app/Contents/MacOS/Google Chrome")
+        candidates = [
-        if mac_chrome.exists():
+            Path("/Applications/Google Chrome.app/Contents/MacOS/Google Chrome"),
-            return str(mac_chrome)
+            Path("/Applications/Microsoft Edge.app/Contents/MacOS/Microsoft Edge"),
+            Path("/Applications/Chromium.app/Contents/MacOS/Chromium"),
+        ]
+        for c in candidates:
+            if c.exists():
+                return str(c)
 
     return None
 
 
 def _open_app_window() -> None:
-    """Wait for the server, then open Chrome in app mode (no address bar)."""
+    """Wait for the server, then open the URL in an --app-mode window.
+
+    --app mode makes the window look like a desktop app (no address bar,
+    no tabs) AND — crucially — makes ``window.close()`` work, because
+    the browser treats --app windows as programmatically closable. The
+    regular-browser fallback prints a warning so the user knows why the
+    Close button on the closing screen will require a manual Ctrl+W.
+    """
     time.sleep(2)
-    chrome = _find_chrome()
+    browser = _find_app_browser()
-    if chrome:
+    if browser:
-        subprocess.Popen([chrome, f"--app={_URL}"])
+        subprocess.Popen([browser, f"--app={_URL}"])
-    else:
+        return
-        # Fallback: open in default browser (will have address bar)
+    print(
+        "DataTools: Chrome and Edge were not found in their standard "
+        "locations. Falling back to the default browser. The Close "
+        "button on the shutdown screen will likely require a manual "
+        "Ctrl+W to close the tab (a browser security restriction "
+        "prevents JavaScript from closing user-opened tabs).",
+        file=sys.stderr,
+    )
     import webbrowser
     webbrowser.open(_URL)
 

src/gui/components/_legacy.py

@@ -159,15 +159,33 @@ _FAREWELL_SCRIPT_TEMPLATE = """
         '</div>';
       return overlay;
     }
+    function tryClose(win) {
+      // Three escalating attempts. Modern browsers only honour close()
+      // for windows that JS opened (Chrome --app windows qualify; a
+      // regular browser tab does not) — there is no JS override for
+      // that policy. The window.open('', '_self') trick used to rewrite
+      // a window's "opener" lineage and let close() through in older
+      // Chrome; modern Chrome patched it but it costs nothing to try.
+      try { win.close(); } catch (e) {}
+      if (win.closed) return;
+      try {
+        var w = win.open('', '_self', '');
+        if (w) {
+          try { w.close(); } catch (e) {}
+        }
+      } catch (e) {}
+      if (win.closed) return;
+      try { win.top.close(); } catch (e) {}
+    }
     function wireClose(doc, win) {
       var btn = doc.getElementById('datatools-close-btn');
       if (!btn) return;
       btn.onclick = function () {
-        try { win.close(); } catch (e) {}
+        tryClose(win);
-        try { win.top.close(); } catch (e) {}
         // If after 250ms the window is still here, the browser
         // blocked the close — show the manual-close hint.
         setTimeout(function () {
+          if (win.closed) return;
           var hint = doc.getElementById('datatools-close-hint');
           if (hint) hint.style.display = 'block';
         }, 250);
@@ -180,9 +198,9 @@ _FAREWELL_SCRIPT_TEMPLATE = """
         doc.body.appendChild(buildOverlay(doc));
       }
       wireClose(doc, win);
-      // Try to close the tab outright too — succeeds in Chrome --app
+      // Auto-close attempt on first paint — succeeds in Chrome --app
       // windows, no-ops on regular tabs.
-      try { win.close(); } catch (e) {}
+      tryClose(win);
     } catch (e) {
       // Cross-origin access denied (shouldn't happen given Streamlit's
       // sandbox flags, but fall back gracefully): cover this iframe.

src/i18n/packs/en.json

@@ -53,7 +53,7 @@
     "farewell_title": "DataTools has shut down",
     "farewell_subtitle": "You can close this window.",
     "close_window_button": "Close this window",
-    "close_hint": "Your browser blocked the close. Press Ctrl+W (or ⌘W on Mac) to close this tab manually."
+    "close_hint": "Your browser is blocking the close — this is a security restriction on tabs you opened yourself, not something we can override. Press Ctrl+W (or ⌘W on Mac) to close this tab. Launch DataTools with python -m src.gui to get an auto-closing app window."
   },
   "close_page": {
     "page_title": "DataTools — Close",

src/i18n/packs/es.json

@@ -53,7 +53,7 @@
     "farewell_title": "DataTools se ha cerrado",
     "farewell_subtitle": "Ya puedes cerrar esta ventana.",
     "close_window_button": "Cerrar esta ventana",
-    "close_hint": "Tu navegador bloqueó el cierre. Presiona Ctrl+W (o ⌘W en Mac) para cerrar esta pestaña manualmente."
+    "close_hint": "Tu navegador está bloqueando el cierre — es una restricción de seguridad para pestañas que abriste tú mismo, no algo que podamos anular. Presiona Ctrl+W (o ⌘W en Mac) para cerrar esta pestaña. Ejecuta DataTools con python -m src.gui para tener una ventana de aplicación que se cierra sola."
   },
   "close_page": {
     "page_title": "DataTools — Cerrar",