Add hypervisor design docs and multinode work log; housekeeping

- docs/hypervisor-design.md, docs/hypervisor_migration.md: unikernel
  runtime design and migration plan (previously untracked)
- log/2026-03-29-mcp-multinode.md: work log (previously untracked)
- CLAUDE.md: mcq lives at a sibling path
- engineering-standards.md: document the push target
- .gitignore: mcdoc checkout; local configs that have held credentials

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

.gitignore

@@ -11,4 +11,12 @@
 /mcns
 /mcp
 /mcdeploy
+/mcdoc
 
+
+# Local service configs and tool settings; these have held credentials.
+/mcat.toml
+/mcq.toml
+/mcr.toml
+/metacrypt.toml
+/.claude/