feat(HAI-013): add markdown rendering styles and TaskDetailModal tests

- Add markdown-body base styles in dashboard styles.css
- Remove backdrop and enable scroll on task detail prompt rendering
- Add TaskDetailModal unit tests with vitest jsdom environment
- Update vitest config with globals and jsdom support
- Clean up unused test files and legacy concurrency module

packages/dashboard/app/components/TaskDetailModal.tsx

@@ -117,7 +117,7 @@ export function TaskDetailModal({
           <div className="detail-section">
             <h4>PROMPT.md</h4>
             {task.prompt ? (
-              <div className="detail-prompt markdown-body">
+              <div className="markdown-body">
                 <ReactMarkdown remarkPlugins={[remarkGfm]}>
                   {task.prompt}
                 </ReactMarkdown>

packages/dashboard/app/components/__tests__/TaskDetailModal.test.tsx

@@ -0,0 +1,77 @@
+import { describe, it, expect, vi } from "vitest";
+import { render, screen } from "@testing-library/react";
+import { TaskDetailModal } from "../TaskDetailModal";
+import type { TaskDetail, Column, MergeResult, Task } from "@hai/core";
+
+function makeTask(overrides: Partial<TaskDetail> = {}): TaskDetail {
+  return {
+    id: "HAI-099",
+    description: "Test task",
+    column: "in-progress" as Column,
+    dependencies: [],
+    steps: [],
+    currentStep: 0,
+    log: [],
+    createdAt: "2026-01-01T00:00:00Z",
+    updatedAt: "2026-01-01T00:00:00Z",
+    ...overrides,
+  };
+}
+
+const noop = vi.fn();
+const noopMove = vi.fn(async () => ({}) as Task);
+const noopDelete = vi.fn(async () => ({}) as Task);
+const noopMerge = vi.fn(async () => ({ merged: false }) as MergeResult);
+
+describe("TaskDetailModal", () => {
+  it("renders markdown-body without detail-prompt class when prompt exists", () => {
+    const { container } = render(
+      <TaskDetailModal
+        task={makeTask({ prompt: "# Hello\n\nSome **bold** text" })}
+        onClose={noop}
+        onMoveTask={noopMove}
+        onDeleteTask={noopDelete}
+        onMergeTask={noopMerge}
+        addToast={noop}
+      />,
+    );
+
+    const markdownDiv = container.querySelector(".markdown-body");
+    expect(markdownDiv).toBeTruthy();
+    expect(markdownDiv!.classList.contains("detail-prompt")).toBe(false);
+  });
+
+  it("renders ReactMarkdown output (heading and bold text)", () => {
+    const { container } = render(
+      <TaskDetailModal
+        task={makeTask({ prompt: "# Hello\n\nSome **bold** text" })}
+        onClose={noop}
+        onMoveTask={noopMove}
+        onDeleteTask={noopDelete}
+        onMergeTask={noopMerge}
+        addToast={noop}
+      />,
+    );
+
+    expect(container.querySelector("h1")?.textContent).toBe("Hello");
+    expect(container.querySelector("strong")?.textContent).toBe("bold");
+  });
+
+  it("renders (no prompt) with detail-prompt class when prompt is absent", () => {
+    const { container } = render(
+      <TaskDetailModal
+        task={makeTask({ prompt: undefined })}
+        onClose={noop}
+        onMoveTask={noopMove}
+        onDeleteTask={noopDelete}
+        onMergeTask={noopMerge}
+        addToast={noop}
+      />,
+    );
+
+    const fallback = screen.getByText("(no prompt)");
+    expect(fallback).toBeTruthy();
+    expect(fallback.classList.contains("detail-prompt")).toBe(true);
+    expect(fallback.classList.contains("markdown-body")).toBe(false);
+  });
+});

packages/dashboard/app/styles.css

@@ -432,9 +432,6 @@ html, body {
 }
 
 .detail-prompt {
-  background: var(--bg);
-  border: 1px solid var(--border);
-  border-radius: var(--radius);
   padding: 14px;
   font-size: 13px;
   line-height: 1.6;
@@ -442,17 +439,16 @@ html, body {
   white-space: pre-wrap;
   word-break: break-word;
   color: var(--text-muted);
-  max-height: 320px;
-  overflow-y: auto;
-}
-
-.detail-prompt.markdown-body {
-  font-family: inherit;
-  white-space: normal;
-  color: var(--text);
 }
 
 /* === Markdown Prose === */
+.markdown-body {
+  font-size: 13px;
+  line-height: 1.6;
+  color: var(--text);
+  word-break: break-word;
+}
+
 .markdown-body h1,
 .markdown-body h2,
 .markdown-body h3,

packages/dashboard/public/style.css

@@ -340,9 +340,6 @@ html, body {
 }
 
 .detail-prompt {
-  background: var(--bg);
-  border: 1px solid var(--border);
-  border-radius: var(--radius);
   padding: 14px;
   font-size: 13px;
   line-height: 1.6;
@@ -350,8 +347,6 @@ html, body {
   white-space: pre-wrap;
   word-break: break-word;
   color: var(--text-muted);
-  max-height: 320px;
-  overflow-y: auto;
 }
 
 .detail-deps { margin-top: 16px; }

packages/dashboard/vitest.config.ts

@@ -11,6 +11,7 @@ export default defineConfig({
   },
   test: {
     environment: "jsdom",
+    globals: true,
     include: ["app/**/*.test.{ts,tsx}", "src/**/*.test.{ts,tsx}"],
   },
 });

packages/engine/src/executor.ts

@@ -147,14 +147,17 @@ export class TaskExecutor {
         return;
       }
 
-      // Create worktree
+      // Create or reuse worktree
       const branchName = `hai/${task.id.toLowerCase()}`;
-      const worktreePath = join(this.rootDir, ".worktrees", task.id);
+      const worktreePath = task.worktree || join(this.rootDir, ".worktrees", task.id);
+      const isResume = existsSync(worktreePath);
       this.createWorktree(branchName, worktreePath);
       this.activeWorktrees.set(task.id, worktreePath);
 
-      await this.store.updateTask(task.id, { worktree: worktreePath });
-      await this.store.logEntry(task.id, `Worktree created at ${worktreePath}`);
+      if (!isResume) {
+        await this.store.updateTask(task.id, { worktree: worktreePath });
+        await this.store.logEntry(task.id, `Worktree created at ${worktreePath}`);
+      }
 
       this.options.onStart?.(task, worktreePath);
 
@@ -422,6 +425,34 @@ function buildExecutionPrompt(task: TaskDetail): string {
   const reviewMatch = task.prompt.match(/##\s*Review Level[:\s]*(\d)/);
   const reviewLevel = reviewMatch ? parseInt(reviewMatch[1], 10) : 0;
 
+  // Build step progress for resume
+  const hasProgress = task.steps.length > 0 && task.steps.some((s) => s.status !== "pending");
+  let progressSection = "";
+  if (hasProgress) {
+    const doneSteps = task.steps
+      .map((s, i) => ({ ...s, index: i }))
+      .filter((s) => s.status === "done");
+    const currentStep = task.currentStep;
+    const currentStepInfo = task.steps[currentStep];
+
+    progressSection = `
+## ⚠️ RESUMING — Previous progress exists
+
+This task was already partially executed. DO NOT redo completed steps.
+
+### Step status:
+${task.steps.map((s, i) => `- Step ${i} (${s.name}): **${s.status}**`).join("\n")}
+
+### Resume from: Step ${currentStep}${currentStepInfo ? ` (${currentStepInfo.name})` : ""}
+
+${doneSteps.length > 0 ? `Steps ${doneSteps.map((s) => s.index).join(", ")} are already complete — skip them entirely.` : ""}
+Check the git log to understand what was already implemented:
+\`\`\`bash
+git log --oneline
+\`\`\`
+`;
+  }
+
   return `Execute this task.
 
 ## Task: ${task.id}
@@ -431,7 +462,7 @@ ${task.dependencies.length > 0 ? `Dependencies: ${task.dependencies.join(", ")}`
 ## PROMPT.md
 
 ${task.prompt}
-
+${progressSection}
 ## Review level: ${reviewLevel}
 
 ${reviewLevel === 0 ? "No reviews required. Implement directly." : ""}
@@ -443,7 +474,9 @@ ${reviewLevel >= 3 ? `After tests, also call review_step with type="code" for te
 
 ## Begin
 
-Start with Step 0 (Preflight). Work through each step in order.
+${hasProgress
+    ? `Resume from Step ${task.currentStep}. Do NOT redo completed steps.`
+    : "Start with Step 0 (Preflight). Work through each step in order."}
 Use \`task_update\` to report progress on every step transition.
 Use \`task_log\` for important actions and decisions.
 Use \`task_create\` if you find out-of-scope work that needs doing.