#rss subcommands on the command channel: help / add <url> <name> /
remove <name> / tags / sources / get <name|#tag>. Sources are stored in
a new rss_sources table in the existing MESH_DB_PATH file (second
node:sqlite connection, case-insensitive names); feeds parsed with
fast-xml-parser (RSS 2.0 + Atom); AI tags and headline summaries via
injected LlmService.chat() with bounded maxTokens (50/200).
CommandService gains prefix registration so one handler owns the whole
#rss family while #ping stays an exact match; wired in CommandModule's
factory — still no constructor-level cycle, no forwardRef. One dead feed
does not sink a tag summary.
