feat(maestro): web spawn form stops naming sessions

The name field starts empty and the reroll is gone; the worktree branch keeps
a default by borrowing one handle from /api/names. A card whose name the
daemon generated renders dimmed until a first prompt settles it.

Refs #131

web/src/styles.css

@@ -1200,6 +1200,14 @@ textarea {
   white-space: nowrap;
 }
 
+/* #131: a name the daemon generated at spawn is provisional — the first prompt
+   may replace it — so it reads as placeholder text rather than a chosen name.
+   A session that never prompts simply keeps it, dimmed; that is accurate. */
+.leaf-name.is-provisional {
+  color: var(--muted);
+  font-weight: 400;
+}
+
 /* Inline rename field (#125): sits exactly where the name it replaces did, so
    the card does not jump when the edit starts. */
 input.leaf-rename {