docs(handover): synthesis — tight TODO + STATE + design-origin conversation

Merges the four Desktop coord-MCP handover documents into two tight
ones and archives the raw design-origin conversation in-repo.

Added:
- docs/handover/COORD-MCP-TODO.md — tight actionable backlog, P0→P4,
  with agreed decisions D1-D4 (DataExpr refactor, .machine_readable/6a2/
  canonical, wait on cartridge-install, revert probe-timing sidecars)
- docs/handover/COORD-MCP-STATE.md — where we are now vs forward vision,
  per-layer status, 38 decisions summarised, Byzantine/self-assessment
  mechanism status, deferred phases 1b/2/3/4
- docs/handover/COORD-DESIGN-ORIGIN-CONVERSATION.txt — raw conversation
  that seeded the design (BFT safety, affinity routing, chief-of-staff
  model) — historical reference

Updated:
- docs/handover/README.md — index now points to the two summaries
  first; full design log + prompt files are the deeper reference.

D4 executed: canonical-proof-suite probe-timing sidecars reverted in
007-lang this session (git checkout --).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath