Add hover tooltips for clipped model names (#1982) (#1985)

Long model names are truncated with ellipsis in two places with no way to see
the full name: the model-picker dropdown items and the chat-header model
indicator. Add a native title tooltip carrying the full name to both — the
dropdown item's name span (nameSpan.title = m.display) and the header label
(label.title = the full model id; empty for the 'Select model' placeholder).

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_model_name_tooltip.py

@@ -0,0 +1,26 @@
+"""Regression for issue #1982 — long model names are clipped with ellipsis in
+two surfaces (the model-picker dropdown items and the chat-header model
+indicator) with no tooltip, so the suffix/variant tag is undiscoverable.
+
+The fix adds a `title` (native hover tooltip) carrying the full name to both
+render sites in static/js/modelPicker.js. The module pulls in browser globals so
+it can't be imported under node; this guards the two title assignments at source.
+"""
+import re
+from pathlib import Path
+
+SRC = (Path(__file__).resolve().parent.parent / "static/js/modelPicker.js").read_text(encoding="utf-8")
+
+
+def test_dropdown_item_has_title_tooltip():
+    # The dropdown item name span must carry a title with the full display name.
+    assert re.search(r"nameSpan\.title\s*=\s*m\.display", SRC), \
+        "dropdown model-name span needs a title tooltip (#1982)"
+
+
+def test_header_indicator_has_title_tooltip():
+    # updateModelPicker must set the header label's title to the full model id
+    # (empty for the 'Select model' placeholder).
+    body = SRC[SRC.index("export function updateModelPicker()"):]
+    assert re.search(r"label\.title\s*=\s*modelId\b", body), \
+        "header model indicator needs a title tooltip (#1982)"