Stage M-A: manual messaging words -- CHANNEL, CHANNEL-CLOSE, JOIN/UNJOIN, JOIN-VM/LEAVE-VM, PUBLISH, INJECT, MAIL?, .MAIL, .CHANNELS (FABRIC-3.9.0 §7.2)

- Eleven words in repl.c over the existing kernel-Hermes C API, registered
  for every VM; `from` always derived in C. Names as ruled (M-1) except
  UNJOIN for LEAVE, which is FORTH-79's DO-loop exit (Captain Bob).
- INJECT (M-2) sends as the root, funded from Hera's reservoir, as new
  type 31; pinned STRICT in kernel_main.c beside BIRTH.
- Read-only accessors sk_hermes_pending_at() / sk_hermes_channel_member_at()
  for .MAIL / .CHANNELS.

Console evidence identical on amd64/aarch64/riscv64: PUBLISH delivers 2
(both print), LEAVE-VM then PUBLISH delivers 1, INJECT shows in MAIL?/.MAIL
as type 31 from Hera before the recipient runs, CHANNEL-CLOSE succeeds and
refuses channel 0, JOIN/UNJOIN, refusals 0/-1. dict_hash set changes by the
11 words (542 words) and is identical across ISAs; acceptance passes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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