Add .wpcignore support, progress indicators, and timeout handling

[noelsaw1]

Problem

WPCC stalls when scanning large directories due to the Magic String Detector phase processing too many files without progress feedback or timeout handling.

Specific Issue: When scanning AI-DDTK (which embeds WPCC via git subtree), the scanner processes 10K+ files including .git/ history and embedded tool code, causing indefinite hangs.

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Requested Features

1. .wpcignore File Support (Priority: High)

Add support for .wpcignore file (like .gitignore) to exclude directories/files from scanning.

Implementation:

• Read .wpcignore from project root during file discovery
• Support glob patterns (same syntax as .gitignore)
• Default exclusions: .git/, node_modules/, vendor/, dist/logs/, dist/reports/

Example .wpcignore:

# Version control
.git/
.svn/

# Dependencies
node_modules/
vendor/

# Build artifacts
dist/
build/
*.min.js
*.min.css

# WPCC output
dist/logs/
dist/reports/

2. Progress Indicators (Priority: Medium)

Show real-time progress during long scans:

• File count: [Magic String Detector] Processing 1234/5678 files...
• Time elapsed: Elapsed: 45s
• Estimated remaining: Est. remaining: 30s

3. Timeout Handling (Priority: Medium)

Add configurable timeouts to prevent indefinite hangs:

• Per-phase timeout (default: 60s)
• Total scan timeout (default: 300s)
• Graceful degradation: skip slow phases, continue with partial results
• CLI flag: --timeout <seconds>

4. Performance Optimization (Priority: Low)

• Cache Magic String Detector results per file hash
• Skip unchanged files on subsequent scans
• Parallelize file processing where possible

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Success Criteria

• .wpcignore file support implemented and documented
• Progress indicators show during all scan phases
• Timeout handling prevents indefinite hangs
• Scanning large directories (10K+ files) completes or times out gracefully
• Documentation updated in README and _AI_INSTRUCTIONS.md

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Workaround (Current)

Users can manually exclude directories using CLI flags:

wpcc --paths . --exclude "tools/,.git/,node_modules/" --format json

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Related

• Tracking issue in AI-DDTK: Add .wpcignore support and performance improvements to WPCC AI-DDTK-Fix-Iterate-Loop#5
• AI-DDTK includes .wpcignore template ready for this feature
• See AI-DDTK BACKLOG.md for detailed implementation plan