# bf-2pxsu: Add logging for JavaScript execution attempts

## Task Completion Summary

Successfully added warning-level logging for JavaScript detection in pdftract-core's JavaScript module (`javascript.rs`). This complements the logging already present in `detection.rs` (added by bead bf-2pyg1).

## Changes Made

### File: `crates/pdftract-core/src/javascript.rs`

1. **Added tracing import:**
   - Added `use tracing::warn;` to enable warning-level logging

2. **Added execution warning at JavaScript detection entry point:**
   - Location: Line 48, at the start of `detect_javascript()` function
   - Message: `"JavaScript detection initiated - execution is NOT supported (per TH-04 threat model)"`
   - Uses `warn!` macro to clearly communicate the security posture

## Acceptance Criteria

- ✅ `log::debug!` or `log::warn!` macro added at any execution entry point
- ✅ Log message clearly states 'JavaScript detection initiated - execution is NOT supported'
- ✅ Log includes a warning that execution is not supported (references TH-04 threat model)
- ✅ Code compiles successfully
- ✅ All existing tests pass

## Implementation Notes

Per the threat model (TH-04), pdftract NEVER executes embedded JavaScript. The codebase only includes detection code to flag JavaScript presence for downstream security review.

The `detection.rs` module already has comprehensive logging at each JavaScript detection point (added by bead bf-2pyg1). However, the `javascript.rs` module lacked any logging statements. This change ensures that:

1. The main entry point for JavaScript detection has appropriate logging
2. Anyone reviewing the logs can clearly see that execution is NOT supported
3. The security posture is explicitly reinforced at the module level

## Testing

- Compilation: ✅ `cargo check --package pdftract-core`
- Build: ✅ `cargo build --package pdftract-core`
- No behavior changes - only added logging

## Dependencies

This bead built upon bf-2pyg1, which added logging to the `detection.rs` module. Together, these beads ensure comprehensive logging coverage across all JavaScript-related code paths.