feat: add two-level work mode (projectExecution + roleExecution) (#15) (#18)

Replaces single 'workMode' with two distinct settings:

1. Plugin-level 'projectExecution' (parallel | sequential)
   - parallel: each project can have active workers independently
   - sequential: only one project can have active workers at a time

2. Project-level 'roleExecution' (parallel | sequential)
   - parallel: DEV and QA can run simultaneously on same project
   - sequential: only one role (DEV or QA) active at a time per project

Changes:
- index.ts: rename workMode → projectExecution in config schema
- projects.ts: add roleExecution field to Project type
- heartbeat_tick: check both levels before picking up tasks
- task_pickup: enforce roleExecution when picking up manually
- project_register: accept roleExecution param (default: parallel)
- devclaw_setup: accept projectExecution param

All defaults remain 'parallel' for backward compatibility.

lib/setup.ts

@@ -32,6 +32,8 @@ export type SetupOpts = {
   workspacePath?: string;
   /** Model overrides per tier. Missing tiers use defaults. */
   models?: Partial<Record<Tier, string>>;
+  /** Plugin-level project execution mode: parallel or sequential. Default: parallel. */
+  projectExecution?: "parallel" | "sequential";
 };
 
 export type SetupResult = {
@@ -110,7 +112,7 @@ export async function runSetup(opts: SetupOpts): Promise<SetupResult> {
   }
 
   // Write plugin config to openclaw.json (includes agentId in devClawAgentIds)
-  await writePluginConfig(models, agentId);
+  await writePluginConfig(models, agentId, opts.projectExecution);
 
   // --- Step 3: Workspace files ---
 
@@ -284,6 +286,7 @@ async function resolveWorkspacePath(agentId: string): Promise<string> {
 async function writePluginConfig(
   models: Record<Tier, string>,
   agentId?: string,
+  projectExecution?: "parallel" | "sequential",
 ): Promise<void> {
   const configPath = path.join(
     process.env.HOME ?? "/home/lauren",
@@ -303,6 +306,11 @@ async function writePluginConfig(
   // Write models
   config.plugins.entries.devclaw.config.models = { ...models };
 
+  // Write projectExecution if specified
+  if (projectExecution) {
+    config.plugins.entries.devclaw.config.projectExecution = projectExecution;
+  }
+
   // Configure subagent cleanup interval to 30 days (43200 minutes)
   // This keeps development sessions alive during active development
   if (!config.agents) config.agents = {};