fix(jira-knowledge): replace hover tooltip with click-based popup for help button

Native Qt tooltips on macOS are unreliable (delayed or invisible). Replace
with a QFrame popup that appears on click, positioned below the ? button,
and closes when clicking elsewhere (Qt.Popup flag handles ESC and outside-click).

- Store help text in self._help_text instead of setToolTip()
- Add _toggle_help_popup() method: creates/destroys floating QFrame
- Update test to check _help_text attribute instead of toolTip()

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/ui/test_jira_knowledge_help_ux.py

@@ -51,15 +51,16 @@ def test_help_icon_exists(dialog):
 
 
 def test_help_icon_has_tooltip(dialog):
-    """Help icon must have a non-empty tooltip with both Project ID and Jira Key explanations."""
+    """Help icon must store help text with both Project ID and Jira Key explanations."""
     from PySide6.QtWidgets import QToolButton
     dlg = dialog
     help_icons = dlg.findChildren(QToolButton)
     assert help_icons, "No help button found"
-    tooltip = help_icons[0].toolTip()
-    assert tooltip, "Help button has no tooltip"
-    assert "Project ID" in tooltip, "Tooltip missing Project ID explanation"
-    assert "Jira Key" in tooltip, "Tooltip missing Jira Key explanation"
+    # Help text is stored in _help_text for click-based popup
+    help_text = getattr(dlg, '_help_text', '') or help_icons[0].toolTip()
+    assert help_text, "Help button has no help content"
+    assert "Project ID" in help_text, "Help content missing Project ID explanation"
+    assert "Jira Key" in help_text, "Help content missing Jira Key explanation"
 
 
 # ---- Help text content ----------------------------------------------------