Add 'hq task workdir' command for displaying task working directories

Implements the task workdir command requested in issue #644. The command
displays working directories for selected tasks within a specific job.

Features:
- CLI output showing task-specific working directories
- JSON output with task_id -> workdir mapping
- Quiet output mode support
- Supports task ID arrays and ranges
- Job selector supports "last" and specific job IDs
- Resolves task-specific working directory paths
- Integrates with existing task selection mechanisms

Usage:
- hq task workdir <job_selector> <task_selector>
- hq task workdir 1 2
- hq task workdir last 1-5
- hq task workdir 2 1,3,5

The implementation reuses the existing task path resolution system to
provide accurate working directory information for individual tasks,
complementing the job-level workdir command.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Kobzol

crates/hyperqueue/src/client/task.rs

@@ -27,6 +27,8 @@ pub enum TaskCommand {
     Info(TaskInfoOpts),
     /// Explain if task can run on a selected worker
     Explain(TaskExplainOpts),
+    /// Display working directory of selected task(s)
+    Workdir(TaskWorkdirOpts),
 }
 
 #[derive(clap::Parser)]
@@ -65,6 +67,16 @@ pub struct TaskExplainOpts {
     pub task_id: JobTaskId,
 }
 
+#[derive(clap::Parser)]
+pub struct TaskWorkdirOpts {
+    /// Select specific job
+    #[arg(value_parser = parse_last_single_id)]
+    pub job_selector: SingleIdSelector,
+
+    /// Select specific task(s)
+    pub task_selector: IntArray,
+}
+
 pub async fn output_job_task_list(
     gsettings: &GlobalSettings,
     session: &mut ClientSession,
@@ -200,3 +212,45 @@ pub async fn output_job_task_explain(
         .print_explanation(response.task_id, &response.explanation);
     Ok(())
 }
+
+pub async fn output_job_task_workdir(
+    gsettings: &GlobalSettings,
+    session: &mut ClientSession,
+    opts: TaskWorkdirOpts,
+) -> anyhow::Result<()> {
+    let task_selector = TaskSelector {
+        id_selector: TaskIdSelector::Specific(opts.task_selector),
+        status_selector: TaskStatusSelector::All,
+    };
+
+    let job_id_selector = match opts.job_selector {
+        SingleIdSelector::Specific(id) => IdSelector::Specific(IntArray::from_id(id)),
+        SingleIdSelector::Last => IdSelector::LastN(1),
+    };
+
+    let message = FromClientMessage::JobDetail(JobDetailRequest {
+        job_id_selector,
+        task_selector: Some(task_selector),
+    });
+    let response =
+        rpc_call!(session.connection(), message, ToClientMessage::JobDetailResponse(r) => r)
+            .await?;
+
+    let jobs = response
+        .details
+        .into_iter()
+        .filter_map(|(job_id, opt_job)| match opt_job {
+            Some(job) => Some((job_id, job)),
+            None => {
+                log::warn!("Job {job_id} not found");
+                None
+            }
+        })
+        .collect();
+
+    gsettings.printer().print_task_workdir(
+        jobs,
+        &response.server_uid,
+    );
+    Ok(())
+}

tests/test_task.py

@@ -77,3 +77,65 @@ def test_long_running_task(hq_env: HqEnv):
     hq_env.start_worker()
     hq_env.command(["submit", "sleep", "20"])
     wait_for_job_state(hq_env, 1, "FINISHED", timeout_s=30)
+
+
+def test_task_workdir_basic(hq_env: HqEnv):
+    """Test basic task workdir functionality."""
+    hq_env.start_server()
+    hq_env.start_worker()
+
+    hq_env.command(["submit", "--array=1-3", "--", "echo", "test"])
+    wait_for_job_state(hq_env, 1, "FINISHED")
+
+    # Test single task workdir
+    output = hq_env.command(["task", "workdir", "1", "2"])
+    assert "Job 1:" in output
+    assert "Task 2:" in output
+
+    # Test multiple tasks workdir
+    output = hq_env.command(["task", "workdir", "1", "1-3"])
+    assert "Job 1:" in output
+    assert "Task 1:" in output
+    assert "Task 2:" in output
+    assert "Task 3:" in output
+
+
+def test_task_workdir_json_output(hq_env: HqEnv):
+    """Test task workdir JSON output."""
+    hq_env.start_server()
+    hq_env.start_worker()
+
+    hq_env.command(["submit", "--array=1-2", "--", "echo", "test"])
+    wait_for_job_state(hq_env, 1, "FINISHED")
+
+    output = hq_env.command(["task", "workdir", "1", "1-2", "--output-mode", "json"])
+    import json
+    data = json.loads(output)
+    
+    assert isinstance(data, list)
+    assert len(data) == 1
+    assert data[0]["job_id"] == 1
+    assert "tasks" in data[0]
+    assert "1" in data[0]["tasks"]
+    assert "2" in data[0]["tasks"]
+
+
+def test_task_workdir_integration_with_task_info(hq_env: HqEnv):
+    """Test that task workdir is consistent with task info."""
+    hq_env.start_server()
+    hq_env.start_worker()
+
+    hq_env.command(["submit", "--array=1-2", "--", "echo", "test"])
+    wait_for_job_state(hq_env, 1, "FINISHED")
+
+    # Get workdir for task
+    workdir_output = hq_env.command(["task", "workdir", "1", "1"])
+    
+    # Get task info
+    info_output = hq_env.command(["task", "info", "1", "1"])
+    
+    # Both should reference working directories
+    import os
+    current_dir = os.getcwd()
+    assert current_dir in workdir_output
+    assert current_dir in info_output