v1.0 PRL Task MVP

Delivered: Configurable PRL task in jsPsych 7.x for Pavlovia — two experiment
modes (combo_action, pick_best_cue), criterion-based reversals, transfer phase,
complete 29-column data output, Playwright E2E validation.

Key accomplishments:
- Config-driven dual-mode architecture from one codebase
- Pure-logic engine with 97 unit tests (zero npm dependencies)
- 29-column complete data output for post-hoc analysis reconstruction
- Full jsPsych experiment deployable to Pavlovia
- Automated E2E validation via Playwright
- Procedural Space Invader pixel-art stimuli

See .planning/MILESTONES.md for full details.