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.

core/config.ts

@@ -0,0 +1,42 @@
+import { homedir } from 'node:os'
+import { resolve as resolvePath } from 'node:path'
+
+export interface SynthesisConfig {
+  bridgePort: number
+  bridgeToken: string
+  claudePluginRef: string
+  permissionMode: string
+  idleKillMs: number
+  maxProcesses: number
+  mappingDbPath: string
+}
+
+const DEFAULTS: SynthesisConfig = {
+  bridgePort: 18801,
+  bridgeToken: 'synthesis-local',
+  claudePluginRef: 'plugin:synthesis-claude@local',
+  permissionMode: 'acceptEdits',
+  idleKillMs: 3_600_000,
+  maxProcesses: 16,
+  mappingDbPath: '~/.openclaw/synthesis/sessions.json',
+}
+
+function expand(p: string): string {
+  if (p.startsWith('~')) return resolvePath(homedir(), p.slice(2))
+  return resolvePath(p)
+}
+
+export function normalizeConfig(raw: unknown): SynthesisConfig {
+  const r = (raw ?? {}) as Partial<SynthesisConfig>
+  const merged: SynthesisConfig = {
+    bridgePort: typeof r.bridgePort === 'number' ? r.bridgePort : DEFAULTS.bridgePort,
+    bridgeToken: typeof r.bridgeToken === 'string' && r.bridgeToken ? r.bridgeToken : DEFAULTS.bridgeToken,
+    claudePluginRef: typeof r.claudePluginRef === 'string' && r.claudePluginRef ? r.claudePluginRef : DEFAULTS.claudePluginRef,
+    permissionMode: typeof r.permissionMode === 'string' && r.permissionMode ? r.permissionMode : DEFAULTS.permissionMode,
+    idleKillMs: typeof r.idleKillMs === 'number' ? r.idleKillMs : DEFAULTS.idleKillMs,
+    maxProcesses: typeof r.maxProcesses === 'number' ? r.maxProcesses : DEFAULTS.maxProcesses,
+    mappingDbPath: typeof r.mappingDbPath === 'string' && r.mappingDbPath ? r.mappingDbPath : DEFAULTS.mappingDbPath,
+  }
+  merged.mappingDbPath = expand(merged.mappingDbPath)
+  return merged
+}