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/tools/project-register.ts

@@ -106,6 +106,11 @@ export function createProjectRegisterTool(api: OpenClawPluginApi) {
           type: "string",
           description: "Deployment URL for the project",
         },
+        roleExecution: {
+          type: "string",
+          enum: ["parallel", "sequential"],
+          description: "Project-level role execution mode: parallel (DEV and QA can work simultaneously) or sequential (only one role active at a time). Defaults to parallel.",
+        },
       },
     },
 
@@ -117,6 +122,7 @@ export function createProjectRegisterTool(api: OpenClawPluginApi) {
       const baseBranch = params.baseBranch as string;
       const deployBranch = (params.deployBranch as string) ?? baseBranch;
       const deployUrl = (params.deployUrl as string) ?? "";
+      const roleExecution = (params.roleExecution as "parallel" | "sequential") ?? "parallel";
       const workspaceDir = ctx.workspaceDir;
 
       if (!workspaceDir) {
@@ -199,6 +205,7 @@ export function createProjectRegisterTool(api: OpenClawPluginApi) {
         baseBranch,
         deployBranch,
         autoChain: false,
+        roleExecution,
         dev: emptyWorkerState([...DEV_TIERS]),
         qa: emptyWorkerState([...QA_TIERS]),
       };