[BUG] [BUG] Agents don't auto-load without restart - breaks user workflow

Summary

New agents created in .claude/agents/ directory are not automatically loaded by Claude Code, requiring users to restart the entire session with /exit and
claude --continue. This creates a frustrating user experience and breaks the thought process flow.

## Problem Description
When users create new agent definition files in .claude/agents/, the agents are not available until Claude Code is restarted. This leads to:

1. Confusing User Experience: Users try to use newly created agents and get no response
2. Broken Workflow: Forces interruption of active work sessions
3. Discovery Time: Takes 4-5 iterations for users to understand the restart requirement
4. Poor Adoption: Users may abandon agent creation due to friction

## Steps to Reproduce

1. Create a new agent file in .claude/agents/new-agent.md
2. Try to use the agent with Task(subagent_type="new-agent", ...)
3. Agent is not recognized/available
4. User must /exit and run claude --continue to reload agents

## Expected Behavior
Option A (Preferred): Agents auto-load when new files are detected
Option B (Minimum): Clear user feedback when agents need restart

## Proposed Solutions

### Immediate Fix (Low Effort)
When an unknown agent is referenced, display helpful message:
⚠️ Agent 'new-agent' not found.
💡 If you just created this agent, restart Claude Code:

1. Type '/exit'
2. Run 'claude --continue'

Available agents: [list current agents]

### Better Solution (Medium Effort)
Implement hot-reloading for agent definitions:

• Watch .claude/agents/ directory for changes
• Automatically reload agent definitions when files are added/modified
• Show confirmation: ✅ Loaded new agent: 'new-agent'

### Ideal Solution (Higher Effort)

• Hot-reload agents automatically
• Provide /reload-agents command for manual refresh
• Show agent status in /agents command (loaded/pending restart)

## Impact

• User Frustration: High - breaks workflow and confuses users
• Adoption Barrier: Medium - reduces willingness to create custom agents
• Support Burden: Medium - likely generates support questions

## Workaround
Users must restart Claude Code session after creating new agents:
```bash
/exit
claude --continue

Environment

• Platform: Cross-platform issue
• Component: Agent loading system
• User Type: All users creating custom agents

Priority Suggestion

Medium-High - Affects user experience and workflow but has workaround

### Step 4: Add Labels (if available)
Select these labels if they exist:

• bug
• ux-improvement
• enhancement
• area:core

Note

• Complete issue is structured by claude-code given problem statement- also explained how to open ( would be more happy if I can create it from claude-code [ will yet to expire gh cli integration ]

this note is written by hand.