feat(bf-2pyg1): add debug logging for JavaScript detection
Add debug logging at JavaScript detection points in pdftract-core:
- Add tracing::{debug, info} imports
- Add info-level logs at each detection point in detect_javascript()
- Add debug-level logs in helper functions (has_js_action, has_js_in_aa)
- Fix page loop iteration to provide page index context in logs
- Include relevant context (page indices, action types, locations)
Verification: notes/bf-2pyg1.md
Tests: All 28 detection tests pass
Acceptance criteria: PASS (compilation, logging, context)
Closes bf-2pyg1