Add targeted regex search tool for specific files

[Copilot]

Implements a new search_regex tool that provides focused regex pattern searching in user-specified files, addressing the need for more targeted searches compared to the existing broad search_text functionality.

Key Features

• Targeted searches: Requires explicit file specification (no default to searching all files)
• Regex pattern matching: Full regex support with proper error handling for invalid patterns
• Context lines: Optional context lines around matches for better understanding
• Output control: Configurable character limits with truncation handling
• Structured response: Consistent metadata format following existing tool conventions

Implementation Details

New Tool: search_regex

# Search for function definitions in specific files
result = await client.call_tool("search_regex", {
    "pattern": "def\\s+\\w+\\(",
    "files": ["main.py", "utils.py"]
})

# Search with context lines for better understanding
result = await client.call_tool("search_regex", {
    "pattern": "class\\s+\\w+",
    "files": ["src/models.py"],
    "context": 3,
    "max_chars": 1000
})

Key Differences from search_text

Feature	search_text	search_regex
File specification	Optional (defaults to all files)	Required (explicit list)
Use case	Broad repository searches	Targeted file searches
Performance	Searches entire repo when no files specified	Efficient - only searches specified files
Error handling	Allows empty file searches	Explicit error for empty file list

Error Handling

The tool provides comprehensive error handling for:

• Invalid regex patterns with detailed error messages
• Non-existent or inaccessible files
• Files outside the authorized root directory
• Empty file lists (explicit requirement)

Testing

• 12 comprehensive test cases covering all functionality and edge cases
• Manual testing verified for real-world usage scenarios
• All existing tests pass - no breaking changes to existing functionality
• Linting passes with project code style requirements

Documentation

Updated README.md with:

• Tool description in the available tools section
• Usage examples showing common patterns
• Integration with existing exploration tools

This addresses the performance and usability concerns when users know exactly which files they want to search, providing a more efficient alternative to broad repository searches.

Fixes #29.

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[codecov]

Codecov Report

Attention: Patch coverage is 93.65079% with 4 lines in your changes missing coverage. Please review.

Project coverage is 93.12%. Comparing base (aa27f53) to head (1c6a77d).

Files with missing lines	Patch %	Lines
dev_kit_mcp_server/tools/explore/search_regex.py	93.44%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #30      +/-   ##
==========================================
+ Coverage   93.09%   93.12%   +0.03%     
==========================================
  Files          33       34       +1     
  Lines         811      873      +62     
==========================================
+ Hits          755      813      +58     
- Misses         56       60       +4     

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[EH-MLS]

@copilot can we simplify this? make shorter and simpler?

[EH-MLS]

Suggested change

context: Number of context lines to include before/after matches (optional)

no need for context param

[Copilot]

Removed the context parameter and simplified the implementation as requested. The tool now provides a cleaner, more focused regex search without context lines. All tests updated and passing. Changes in commit 1c6a77d.

[Copilot]

@copilot can we simplify this? make shorter and simpler?

Simplified the search_regex implementation by removing the context parameter and related complexity. The tool now provides a cleaner, more focused regex search with simpler output format. Changes in commit 1c6a77d.