feat(custom-buffer-file): extend buffer-source dispatch to mu4e and Info

Add two dispatchers to cj/buffer-source-functions so C-; b p yields a
useful link form in two more major modes.

mu4e-view-mode returns "mu4e:msgid:<id>" so the result pastes into org
as a clickable link and matches mu4e's own org-protocol handler.
Falls through to buffer-file-name when point isn't on a real message.

Info-mode returns "info:(manual)node" -- the form org-info-store-link
produces.  file-name-base only strips one extension, so a compressed
"emacs.info.gz" comes back as "emacs.info"; trim the trailing ".info"
to get the bare manual name.  Falls through when Info hasn't populated
its current-file / current-node vars yet.

Tests cover normal + boundary fallthrough for each new mode.

0 files changed, 0 insertions, 0 deletions