release(v4.7.3): bump framework and eight skills to 4.7.3 in lockstep; archive PR #37 merge-side reviews

Issue #36: delegated prompts travel by file, a delegation that fails ends
the loop with rc 1. VERSIONS.md carries the entry; the merge-side reports
(round 1 @59be1c8 and round 2 @708262a with identity sidecars, base
59be1c8 -> head 708262a, evidence review-tree) are archived under
.agents/reports/<session>/.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff

.agents/skills/multi-agent-mux-create/SKILL.md

@@ -1,7 +1,7 @@
 ---
 name: multi-agent-mux-create
 description: "Create a new agent session (claude, antigravity/agy) in a dedicated herdr session for context-preserving long-running work. Always creates a herdr session — never backgrounds with nohup/disown. Writes the new session to .mam/agent-sessions.yaml. Use when you want to start a fresh agent (no prior UUID) for a new project workspace."
-version: 4.7.2
+version: 4.7.3
 author: godopu
 license: MIT
 platforms: [linux, macos]