[BUG] Deleted Agents Still Consume Tokens and Bloat Context Window

## Description
Agent definitions in the Task tool continue to consume significant context window space even after
the agent files are deleted from .claude/agents/. This causes unnecessary context window bloat and
degrades performance.

## Steps to Reproduce

1. Start with 29 agents in .claude/agents/ folder
2. Delete/move most agent files (e.g., keep only 5 agents)
3. Start a NEW Claude Code session
4. Check context window usage - all 29 original agents still loaded
5. Each deleted agent still consumes ~100-300 tokens in Task tool definition

## Impact

• Context Window Bloat: 15-20% of context window wasted on non-existent agents
• Performance: Performance degradation because of context window bloat
• Scalability: Adding more agents permanently increases context usage

## Expected Behavior

• Task tool should only load agents that exist in .claude/agents/
• Deleted agents should free up context window space
• Context usage should scale with actual agent count

## Actual Behavior

• All historical agents remain in Task tool definition
• Context window permanently bloated with deleted agent descriptions
• No way to reclaim context space without modifying Claude Code itself

## Example
Current state:

• 5 agents in .claude/agents/ folder
• 29 agents in Task tool definition
• ~3,000 tokens wasted on 24 non-existent agents
• 20% of context window consumed by tools (should be ~5%)

## Suggested Solutions

1. Dynamically generate Task tool from .claude/agents/ directory
2. Load agent definitions on-demand rather than persist
3. Implement context window optimization for large codebases
4. Add command to manually refresh/optimize tool definitions