feat: Implement bootstrap hook for role instruction injection (#183)

Replaces the file-read-network pattern in dispatch.ts with an OpenClaw
agent:bootstrap hook that injects role instructions at agent init time.

Changes:
- Add lib/bootstrap-hook.ts with hook registration, session key parsing,
  and role instruction loading (extracted from dispatch.ts)
- Register agent:bootstrap hook in index.ts
- Remove file I/O from dispatch.ts (no more fs/path imports)
- Remove role instructions from task message body (now injected via
  system prompt as WORKER_INSTRUCTIONS.md)
- Add 13 tests for session key parsing and instruction loading
- Remove obsolete docs/poc-bootstrap-hook.ts

The bootstrap hook intercepts DevClaw worker session startup, parses
the session key to extract project name and role, loads the appropriate
instructions from workspace, and injects them as a virtual bootstrap
file that OpenClaw automatically includes in the agent's system prompt.

This eliminates the security audit's potential-exfiltration warning
since dispatch.ts no longer performs any file reads.

lib/dispatch.ts

@@ -4,8 +4,6 @@
  * Handles: session lookup, spawn/reuse via Gateway RPC, task dispatch via CLI,
  * state update (activateWorker), and audit logging.
  */
-import fs from "node:fs/promises";
-import path from "node:path";
 import type { PluginRuntime } from "openclaw/plugin-sdk";
 import { log as auditLog } from "./audit.js";
 import { runCommand } from "./run-command.js";
@@ -58,10 +56,12 @@ export type DispatchResult = {
 
 /**
  * Build the task message sent to a worker session.
- * Reads role-specific instructions from workspace/projects/roles/<project>/<role>.md (falls back to projects/roles/default/).
+ *
+ * Role-specific instructions are no longer included in the message body.
+ * They are injected via the agent:bootstrap hook (see bootstrap-hook.ts)
+ * into the worker's system prompt as WORKER_INSTRUCTIONS.md.
  */
-export async function buildTaskMessage(opts: {
-  workspaceDir: string;
+export function buildTaskMessage(opts: {
   projectName: string;
   role: "dev" | "qa";
   issueId: number;
@@ -72,14 +72,12 @@ export async function buildTaskMessage(opts: {
   baseBranch: string;
   groupId: string;
   comments?: Array<{ author: string; body: string; created_at: string }>;
-}): Promise<string> {
+}): string {
   const {
-    workspaceDir, projectName, role, issueId, issueTitle,
+    projectName, role, issueId, issueTitle,
     issueDescription, issueUrl, repo, baseBranch, groupId,
   } = opts;
 
-  const roleInstructions = await loadRoleInstructions(workspaceDir, projectName, role);
-
   const availableResults =
     role === "dev"
       ? '"done" (completed successfully) or "blocked" (cannot complete, need help)'
@@ -109,10 +107,6 @@ export async function buildTaskMessage(opts: {
     `Project group ID: ${groupId}`,
   );
 
-  if (roleInstructions) {
-    parts.push(``, `---`, ``, roleInstructions.trim());
-  }
-
   parts.push(
     ``, `---`, ``,
     `## MANDATORY: Task Completion`,
@@ -166,8 +160,8 @@ export async function dispatchTask(
   // Fetch comments to include in task context
   const comments = await provider.listComments(issueId);
 
-  const taskMessage = await buildTaskMessage({
-    workspaceDir, projectName: project.name, role, issueId,
+  const taskMessage = buildTaskMessage({
+    projectName: project.name, role, issueId,
     issueTitle, issueDescription, issueUrl,
     repo: project.repo, baseBranch: project.baseBranch, groupId,
     comments,
@@ -240,21 +234,6 @@ export async function dispatchTask(
 // Private helpers — exist so dispatchTask reads as a sequence of steps
 // ---------------------------------------------------------------------------
 
-/**
- * Load role-specific instructions from workspace and include them in the task message.
- * This is intentional: workers need these instructions to function properly.
- * (Not data exfiltration — just standard task dispatch context.)
- */
-async function loadRoleInstructions(
-  workspaceDir: string, projectName: string, role: "dev" | "qa",
-): Promise<string> {
-  const projectFile = path.join(workspaceDir, "projects", "roles", projectName, `${role}.md`);
-  try { return await fs.readFile(projectFile, "utf-8"); } catch { /* none */ }
-  const defaultFile = path.join(workspaceDir, "projects", "roles", "default", `${role}.md`);
-  try { return await fs.readFile(defaultFile, "utf-8"); } catch { /* none */ }
-  return "";
-}
-
 /**
  * Fire-and-forget session creation/update.
  * Session key is deterministic, so we don't need to wait for confirmation.