Task tool doesn't display output filename after completion

Bug Description

When using the Task tool to run an agent that creates a file, the agent's output doesn't include the filename or file location where the document was saved.

Steps to Reproduce

1. Use Task tool to launch an agent with a prompt that creates a file
2. Agent completes successfully and creates the file
3. Agent returns text output but doesn't specify the filename or path

Expected Behavior

After creating a file, the agent should clearly report:

• ✅ File created: filename.md
• Location: /path/to/file.md
• File size: XX KB

Actual Behavior

Agent returns extensive text output but doesn't confirm:

• Where the file was saved
• What the file is named
• Whether file creation succeeded

Example

Task(
    description="Create overview document",
    prompt="Create a comprehensive overview and save to IMPLEMENTATION_OVERVIEW.md in the docs directory",
    subagent_type="general-purpose"
)

Agent Output: Returns 10,000+ words of content but doesn't confirm:

• Filename
• Location
• Success status

User had to manually check directory to find the created file.

Impact

• Usability: User doesn't know where to find the created file
• Confirmation: No confirmation that file was actually created
• Workflow: Breaks flow by requiring manual verification

Suggested Fix

Agent should always include in final output:

✅ File created: IMPLEMENTATION_OVERVIEW.md (69 KB)
Location: /project/docs/IMPLEMENTATION_OVERVIEW.md

Environment

• Claude Code: Latest version
• Task tool: general-purpose agent
• Operation: File creation via Write tool

Additional Context

This is a usability issue that affects workflow efficiency when working with agents that create files. The lack of filename confirmation requires manual directory checking to verify file creation and location.