The files panel and the Claude Config tab called ipc.request('editor.open')
for every file, which targets the editor — so a .md click never reached the
right-side markdown reader (it opens only when something publishes
('builtin.markdown','selection')). Route .md clicks from the files panel
(tree + filtered rows), the Config tab's file-backed rows, and .md wiki links
in the viewer to that channel; non-.md files still open in the editor. Also
remove the dead DaemonEvent fallback that listened for 'editor.buffer_activated'
(the registry emits 'editor.active-changed').
T-187.
Co-Authored-By: Claude <noreply@anthropic.com>
