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/ast-parser.js

@@ -2,7 +2,7 @@ const LINE_RE = /^(\d{2}) (\S+(?:\.\S+)*) ?(.*)/;
 const DEBUG_RE = /^\d{2} # DEBUG/;
 
 
-function coerce(s) {
+export function coerce(s) {
     if (s === 'True' || s === 'Y' || s === 'on' || s === 'true') return true;
     if (s === 'False' || s === 'N' || s === 'off' || s === 'false') return false;
     if (s === '') return s;