ui: named FCI block holds the metadata; hide the empty content pane (v2.7.13)

- pysimFsInfoHtml puts the FID/type/size line inside the fieldset, so the
  selected file is one bordered block with its symbolic name in the border;
  files without an FCI keep the plain borderless line.
- The content pane starts hidden and is synced after every mutation
  (selection clears it, read success shows it, read failure keeps it hidden,
  edit/cancel re-sync): no empty box before a read or edit.
- tests: FCI ordering assertions; new fs_read.test.js (visibility helper,
  read success/failure/throw, markup + call sites); fs_edit extraction.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "pysim-simple-server"
-version = "2.7.12"
+version = "2.7.13"
 description = "HTTP REST server wrapping pysim for the SIMple PWA"
 requires-python = ">=3.8"
 # pysim is a git-only dependency installed explicitly by setup.bat/setup.sh.