BA pane: group bars by P?L? key, render as inline chips

Bars in the BA sub-objects pane are now visually grouped by the
P\d+L\d+ fragment extracted from their opaque IDs (e.g. P1L1, P2L3).
Each group renders as a row of compact inline-block chips; groups are
separated by a line break. Fallback: if an ID contains no P?L?
pattern, trailing digits are stripped instead, yielding singleton rows.

The grouping is a display-only heuristic — no semantic meaning is
derived from the ID. Chips are clickable, highlight when focused.

static/style.css

@@ -308,6 +308,41 @@
     font-family: monospace;
 }
 
+/* Bar sub-objects: grouped by P?L? key, chips inline per group */
+.se-bar-groups {
+    padding: 0.2rem 0;
+}
+
+.se-bar-group {
+    padding: 0.15rem 0.1rem;
+    border-bottom: 1px solid #1e1e1e;
+    line-height: 1.8;
+}
+
+.se-bar-chip {
+    display: inline-block;
+    font-size: 0.7rem;
+    font-family: monospace;
+    padding: 0.1rem 0.25rem;
+    border: 1px solid #383838;
+    background: #1e1e1e;
+    color: #777;
+    cursor: pointer;
+    margin: 1px;
+    line-height: 1.4;
+}
+
+.se-bar-chip:hover {
+    color: #ccc;
+    border-color: #555;
+}
+
+.se-bar-chip.focused {
+    background: #1a3a5a;
+    color: #ddd;
+    border-color: #4a7aaa;
+}
+
 /* Export log (shown in CP pane after export) */
 .se-export-log {
     font-size: 0.75rem;