chore: initial scaffolding for SynthesisAgent.OpenclawPlugin

OpenClaw plugin that manages long-lived interactive Claude Code processes
per OpenClaw session. Process manager + session-mapping persistence +
bridge WebSocket server skeleton.

Will be rewritten to follow the contractor-agent HTTP model-provider pattern
(register as `synthesis-claude-bridge` provider, receive /v1/chat/completions,
dispatch to channel notification on the bound Claude process). See parent
repo's STATUS.md for the punch list.

README.md

@@ -0,0 +1,73 @@
+# SynthesisAgent.OpenclawPlugin
+
+The **OpenClaw side** of SynthesisAgent. Lives inside the OpenClaw process; spawns and manages one long-lived interactive `claude` per OpenClaw session.
+
+## Components
+
+```
+index.ts                 entry: definePluginEntry, wires up the others
+core/config.ts           plugin config schema + defaults
+core/session-mapping.ts  persistent openclaw_session ↔ claude_session_uuid
+core/process-manager.ts  spawn/resume/kill claude processes
+core/cli.ts              admin commands (`openclaw synthesis ...`)
+web/bridge-server.ts     WebSocket server that ClaudePlugins connect into
+```
+
+## Lifecycle
+
+```
+plugin loaded
+  ↓
+SessionMapping reads ~/.openclaw/synthesis/sessions.json
+ProcessManager idle, no spawns yet
+BridgeServer binds 127.0.0.1:18801
+  ↓
+inbound Discord msg for session=alice
+  ↓
+processManager.ensure('alice')
+  - mapping.ensure → claude_session_uuid (new or existing)
+  - spawn `claude --channels plugin:synthesis-claude@local --resume <uuid> ...`
+  - inject env: SYNTHESIS_BRIDGE_URL / TOKEN / OPENCLAW_SESSION / CLAUDE_SESSION
+  ↓
+ClaudePlugin (in spawned claude) dials ws://127.0.0.1:18801/bridge
+  - sends hello frame
+  - server validates token, marks process ready, sends hello_ack with tool catalog
+  ↓
+processManager.ensure resolves
+inbound message pushed → notifications/claude/channel → Claude starts new turn
+  ↓
+Claude calls tools/call → forwarded to OpenClaw tool surface
+Claude finishes → process stays alive, idle timer reset
+  ↓
+1 hour idle → idleSweeper SIGTERMs the process
+mapping is preserved → next message resumes via --resume
+```
+
+## Config
+
+See `openclaw.plugin.json` `configSchema`. Override in `~/.openclaw/openclaw.json`:
+
+```json
+{
+  "plugins": {
+    "entries": {
+      "synthesis-agent": {
+        "bridgePort": 18801,
+        "bridgeToken": "<random secret>",
+        "idleKillMs": 1800000,
+        "maxProcesses": 8
+      }
+    }
+  }
+}
+```
+
+## TODO
+
+- [ ] Discover exact OpenClaw plugin-sdk API for: inbound event subscription, CLI command registration, tool catalog enumeration. See `contractor-agent/index.ts` for current best example.
+- [ ] Wire `api.channels.onInbound(...)` to `pm.ensure()` + `bridgeServer.pushInbound()`.
+- [ ] Implement tool dispatch in `web/bridge-server.ts` (current `tool_call` handler returns not-implemented).
+- [ ] Implement permission routing back to source channel.
+- [ ] CLI: `openclaw synthesis list`, `push`, `kill`, `forget`.
+- [ ] Settle path conflict: this plugin needs to live at `/root/.openclaw/plugins/synthesis-agent/` to be auto-loaded. Either symlink from this repo or document copy-install.
+- [ ] Decide policy on `--no-session-persistence` flag (currently we rely on default persistence so `--resume` works).