tests: anchor the account-block match and keep the wildcard in-attribute

Review caught two soft spots in the loosened regex: the broadened pattern
also matched the update-card wrapper, so a broken account block could hide
behind the lookalike, and the \S wildcard could in principle walk across the
closing quote into other markup. The match is now anchored to the
displayTitle span that only the account block contains (bounded, stopping at
any closing div), and every wildcard is restricted to non-quote characters
so it can never leave the className attribute. Verified exactly one match at
the account block on current sources; all three tests pass.

tests/studio/test_studio_text_descender_clipping.py

@@ -34,10 +34,15 @@ def test_model_selector_trigger_label_uses_leading_tight():
 
 def test_sidebar_account_block_uses_leading_tight():
     src = _read(APP_SIDEBAR)
-    # Match the account-block parent div regardless of its gap utility; this
-    # guard is about the leading-* class, not the spacing.
+    # Match the account-block parent div regardless of its gap utility or any
+    # sizing classes between flex and flex-col (min-w-0 flex-1 arrived with the
+    # long-name truncation work); this guard is about the leading-* class only.
+    # [^"\s] keeps the wildcard inside the className attribute, and the trailing
+    # displayTitle anchor pins the match to the account block itself so a
+    # lookalike wrapper (the update card) can never satisfy the guard.
     pattern = re.compile(
-        r'<div\s+className="flex\s+flex-col\s+gap-\S+\s+(\S+)\s+group-data-\[collapsible=icon\]:hidden">',
+        r'<div\s+className="flex\s+(?:[^"\s]+\s+)*?flex-col\s+gap-[^"\s]+\s+([^"\s]+)\s+'
+        r'group-data-\[collapsible=icon\]:hidden">(?:(?!</div>)[\s\S]){0,400}?\{displayTitle\}',
     )
     matches = pattern.findall(src)
     assert matches, "could not find sidebar account-block parent div"