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/bootstrap-hook.test.ts

@@ -0,0 +1,107 @@
+/**
+ * Tests for bootstrap hook session key parsing and instruction loading.
+ * Run with: npx tsx --test lib/bootstrap-hook.test.ts
+ */
+import { describe, it } from "node:test";
+import assert from "node:assert";
+import { parseDevClawSessionKey, loadRoleInstructions } from "./bootstrap-hook.js";
+import fs from "node:fs/promises";
+import path from "node:path";
+import os from "node:os";
+
+describe("parseDevClawSessionKey", () => {
+  it("should parse a standard dev session key", () => {
+    const result = parseDevClawSessionKey("agent:devclaw:subagent:my-project-dev-medior");
+    assert.deepStrictEqual(result, { projectName: "my-project", role: "dev" });
+  });
+
+  it("should parse a qa session key", () => {
+    const result = parseDevClawSessionKey("agent:devclaw:subagent:webapp-qa-reviewer");
+    assert.deepStrictEqual(result, { projectName: "webapp", role: "qa" });
+  });
+
+  it("should handle project names with hyphens", () => {
+    const result = parseDevClawSessionKey("agent:devclaw:subagent:my-cool-project-dev-junior");
+    assert.deepStrictEqual(result, { projectName: "my-cool-project", role: "dev" });
+  });
+
+  it("should handle project names with multiple hyphens and qa role", () => {
+    const result = parseDevClawSessionKey("agent:devclaw:subagent:a-b-c-d-qa-tester");
+    assert.deepStrictEqual(result, { projectName: "a-b-c-d", role: "qa" });
+  });
+
+  it("should return null for non-subagent session keys", () => {
+    const result = parseDevClawSessionKey("agent:devclaw:main");
+    assert.strictEqual(result, null);
+  });
+
+  it("should return null for session keys without role", () => {
+    const result = parseDevClawSessionKey("agent:devclaw:subagent:project-unknown-level");
+    assert.strictEqual(result, null);
+  });
+
+  it("should return null for empty string", () => {
+    const result = parseDevClawSessionKey("");
+    assert.strictEqual(result, null);
+  });
+
+  it("should parse senior dev level", () => {
+    const result = parseDevClawSessionKey("agent:devclaw:subagent:devclaw-dev-senior");
+    assert.deepStrictEqual(result, { projectName: "devclaw", role: "dev" });
+  });
+
+  it("should parse simple project name", () => {
+    const result = parseDevClawSessionKey("agent:devclaw:subagent:api-dev-junior");
+    assert.deepStrictEqual(result, { projectName: "api", role: "dev" });
+  });
+});
+
+describe("loadRoleInstructions", () => {
+  it("should load project-specific instructions", async () => {
+    const tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "devclaw-test-"));
+    const projectDir = path.join(tmpDir, "projects", "roles", "test-project");
+    await fs.mkdir(projectDir, { recursive: true });
+    await fs.writeFile(path.join(projectDir, "dev.md"), "# Dev Instructions\nDo the thing.");
+
+    const result = await loadRoleInstructions(tmpDir, "test-project", "dev");
+    assert.strictEqual(result, "# Dev Instructions\nDo the thing.");
+
+    await fs.rm(tmpDir, { recursive: true });
+  });
+
+  it("should fall back to default instructions", async () => {
+    const tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "devclaw-test-"));
+    const defaultDir = path.join(tmpDir, "projects", "roles", "default");
+    await fs.mkdir(defaultDir, { recursive: true });
+    await fs.writeFile(path.join(defaultDir, "qa.md"), "# QA Default\nReview carefully.");
+
+    const result = await loadRoleInstructions(tmpDir, "nonexistent-project", "qa");
+    assert.strictEqual(result, "# QA Default\nReview carefully.");
+
+    await fs.rm(tmpDir, { recursive: true });
+  });
+
+  it("should return empty string when no instructions exist", async () => {
+    const tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "devclaw-test-"));
+
+    const result = await loadRoleInstructions(tmpDir, "missing", "dev");
+    assert.strictEqual(result, "");
+
+    await fs.rm(tmpDir, { recursive: true });
+  });
+
+  it("should prefer project-specific over default", async () => {
+    const tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "devclaw-test-"));
+    const projectDir = path.join(tmpDir, "projects", "roles", "my-project");
+    const defaultDir = path.join(tmpDir, "projects", "roles", "default");
+    await fs.mkdir(projectDir, { recursive: true });
+    await fs.mkdir(defaultDir, { recursive: true });
+    await fs.writeFile(path.join(projectDir, "dev.md"), "Project-specific instructions");
+    await fs.writeFile(path.join(defaultDir, "dev.md"), "Default instructions");
+
+    const result = await loadRoleInstructions(tmpDir, "my-project", "dev");
+    assert.strictEqual(result, "Project-specific instructions");
+
+    await fs.rm(tmpDir, { recursive: true });
+  });
+});