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.

docs/wire-protocol.md

@@ -0,0 +1,122 @@
+# Wire Protocol — OpenclawPlugin ↔ ClaudePlugin
+
+A WebSocket connection from each spawned ClaudePlugin instance back to OpenclawPlugin's bridge server. JSON messages, one per frame.
+
+## Connection bootstrap
+
+On spawn, OpenclawPlugin sets these env vars on the Claude process so ClaudePlugin can find its way home:
+
+| Env var                        | Purpose                                                       |
+|--------------------------------|---------------------------------------------------------------|
+| `SYNTHESIS_BRIDGE_URL`         | WebSocket URL, e.g. `ws://127.0.0.1:18801/bridge`             |
+| `SYNTHESIS_BRIDGE_TOKEN`       | Shared secret, validated server-side                          |
+| `SYNTHESIS_OPENCLAW_SESSION`   | The OpenClaw session ID this Claude process serves            |
+| `SYNTHESIS_CLAUDE_SESSION`     | The Claude session UUID (for traceability)                    |
+
+ClaudePlugin connects on startup and sends:
+
+```json
+{ "type": "hello",
+  "openclaw_session": "<sid>",
+  "claude_session":   "<uuid>",
+  "pid":              12345,
+  "token":            "<bridge_token>" }
+```
+
+OpenclawPlugin responds with:
+
+```json
+{ "type": "hello_ack", "tools": [ /* tool catalog */ ], "session_meta": { ... } }
+```
+
+If `hello` is rejected (bad token, unknown session), the server closes the socket.
+
+## Direction: OpenClaw → Claude (inbound events)
+
+```json
+{ "type": "inbound_message",
+  "request_id": "msg_abc123",
+  "content": "user message text",
+  "meta": {
+    "chat_id":   "<openclaw_session_id>",
+    "message_id": "...",
+    "user":       "alice",
+    "user_id":    "...",
+    "ts":         "2026-05-14T...Z",
+    "source_channel": "discord",
+    "attachments":    [ ... ]
+  }
+}
+```
+
+ClaudePlugin translates each `inbound_message` into:
+
+```json
+{ "method": "notifications/claude/channel",
+  "params": { "content": ..., "meta": ... } }
+```
+
+…and emits it on its MCP stdio. Claude Code reacts by starting a new turn.
+
+## Direction: OpenClaw → Claude (permission reply)
+
+When the user answers a permission prompt out of band (e.g. "yes abxyz" in Discord), OpenClaw forwards:
+
+```json
+{ "type": "permission_reply",
+  "request_id": "abxyz",
+  "behavior":   "allow" }
+```
+
+ClaudePlugin emits an MCP `notifications/claude/channel/permission` for that request_id.
+
+## Direction: Claude → OpenClaw (tool calls)
+
+Each `tools/call` Claude makes on ClaudePlugin (excluding internal ones the plugin owns) is forwarded over the bridge:
+
+```json
+{ "type": "tool_call",
+  "call_id":  "tc_001",
+  "tool":     "pcexec",
+  "args":     { ... } }
+```
+
+OpenclawPlugin invokes the corresponding OpenClaw tool and responds:
+
+```json
+{ "type": "tool_result",
+  "call_id": "tc_001",
+  "ok":      true,
+  "result":  { ... } }
+```
+
+…or with `"ok": false, "error": "..."`.
+
+## Direction: Claude → OpenClaw (permission request)
+
+When Claude Code asks for a permission via `notifications/claude/channel/permission_request`, ClaudePlugin forwards:
+
+```json
+{ "type": "permission_request",
+  "request_id": "<5 lowercase letters minus 'l'>",
+  "tool":       "Bash",
+  "args":       { ... },
+  "rationale":  "..." }
+```
+
+OpenclawPlugin routes this to the user via the source channel (e.g. posts a Discord message: "Approve? Reply `yes <code>`").
+
+## Direction: bidirectional health
+
+```json
+{ "type": "ping",  "ts": ... }
+{ "type": "pong",  "ts": ... }
+```
+
+OpenclawPlugin sends `ping` every 30s. ClaudePlugin missing 2 consecutive pings → server marks the connection dead, allows reconnect.
+
+## Reconnect semantics
+
+- ClaudePlugin reconnects on socket close with exponential backoff (1s, 2s, 4s, max 30s).
+- During disconnect, OpenclawPlugin buffers up to N inbound messages per session (configurable). Buffer overflow drops the oldest with a warning.
+- On reconnect, the `hello` message re-establishes session binding.