feat(map): enhance dev_map with signatures, hot paths, and smart depth

[prosdev]

Summary

Enhances the dev_map tool to provide richer, more useful codebase overviews for AI assistants.

Changes

1. Signatures in Exports

• Export display now shows function/method signatures instead of just names
• Signatures truncated to 60 chars for readability
• Falls back to name if no signature available

2. Hot Paths (Most Referenced Files)

• New section showing files with most incoming references
• Computed from callers and callees metadata
• Helps AI identify central/important code quickly
• Configurable via includeHotPaths and maxHotPaths options

3. Smart Depth (Adaptive Expansion)

• Information density heuristic for tree pruning
• Expands directories with high component counts
• Collapses sparse directories to save tokens
• Always shows first 2 levels for basic structure
• Configurable via smartDepth and smartDepthThreshold options

Example Output

# Codebase Map

## Hot Paths (most referenced)
1. `packages/core/src/indexer/index.ts` (RepositoryIndexer) - 47 refs
2. `packages/core/src/vector/store.ts` (LanceDBVectorStore) - 32 refs
3. `packages/mcp-server/src/server/mcp-server.ts` (MCPServer) - 28 refs

## Directory Structure

└── packages/ (195 components)
    ├── core/ (45 components)
    │   └── exports: function search(query, opts): Promise<Result[]>, class RepositoryIndexer...
    ├── mcp-server/ (28 components)
    │   └── exports: class MCPServer, function createAdapter(config): Adapter...

New Options

Option	Type	Default	Description
includeHotPaths	boolean	true	Show hot paths section
maxHotPaths	number	5	Max hot paths to display
smartDepth	boolean	false	Use adaptive depth
smartDepthThreshold	number	10	Min components to expand

Testing

• 3 new tests for signatures
• 5 new tests for hot paths
• 3 new tests for smart depth
• All 1370 tests passing