chore: initial scaffolding for SynthesisAgent

Bridge between OpenClaw (multi-channel hub) and interactive Claude Code,
keeping autonomous agent usage on the subscription quota after the
2026-06-15 Agent SDK credit split.

Initial scaffolding only — two submodules with skeletons:

- SynthesisAgent.ClaudePlugin: stdio MCP server registered as a --channels
  source. Declares experimental.claude/channel capability (verified 2026-05-14
  against the official Anthropic discord plugin) and emits
  notifications/claude/channel to push OpenClaw inbound messages into the
  Claude turn loop.

- SynthesisAgent.OpenclawPlugin: process manager + session mapping +
  bridge WebSocket. Currently shaped around a custom ws protocol; will be
  rewritten as a model-provider HTTP server (contractor-agent pattern) so
  OpenClaw routes inbound channel messages through it via /v1/chat/completions.

See STATUS.md for the open punch list and docs/wire-protocol.md for the
(soon-to-change) inter-plugin frame schema.

SynthesisAgent.ClaudePlugin/skills/configure/SKILL.md

@@ -0,0 +1,15 @@
+---
+name: synthesis-status
+description: Inspect the SynthesisAgent channel — current OpenClaw session binding, bridge connection state, pending tool calls
+argument-hint: ""
+allowed-tools: [Bash]
+---
+
+Print SynthesisAgent ClaudePlugin status from the env + bridge:
+
+- `SYNTHESIS_OPENCLAW_SESSION`: which OpenClaw session this Claude process serves
+- `SYNTHESIS_CLAUDE_SESSION`: the resumable Claude session UUID
+- `SYNTHESIS_BRIDGE_URL`: bridge endpoint
+- Bridge health: last `pong` timestamp, pending tool calls
+
+When the user asks "what session am I in?", "is the bridge connected?", or "show synthesis status", read the env vars and report.