PaneCP article label + PaneFO editable property rows

Article entries in the CP path list now show the article label
(letter/extension) instead of just "article", with a property count
in the meta column. In the FO pane, each property is rendered as an
editable row: key input, value input (coerced via ast-parser.coerce),
scope toggle, morphing default/overwrite label, and per-row remove
button. A "+ add property" button appends a blank defaults entry.
Every edit marks the score dirty.

`coerce` is now exported from ast-parser.js so the FO pane can apply
the same type-inference rules to user input as the parser does to
AST values.

static/style.css

@@ -398,3 +398,33 @@
 .se-toggle-label.active {
     color: #d8d8d8;
 }
+
+.se-prop-key, .se-prop-val {
+    background: #1a1a1a;
+    color: #d8d8d8;
+    border: 1px solid #444;
+    border-radius: 0.2rem;
+    padding: 0.15rem 0.3rem;
+    font-family: monospace;
+    font-size: 0.8rem;
+}
+.se-prop-key:focus, .se-prop-val:focus {
+    outline: none;
+    border-color: #7a7a7a;
+    background: #222;
+}
+
+.se-btn-remove {
+    background: transparent;
+    color: #888;
+    border: 1px solid #444;
+    border-radius: 0.2rem;
+    cursor: pointer;
+    padding: 0 0.4rem;
+    font-size: 0.9rem;
+    line-height: 1;
+}
+.se-btn-remove:hover {
+    color: #e06060;
+    border-color: #602020;
+}