docs: drop R4-续 retrospective paragraph — it reintroduced the wrong shaping=0.5 value

docs: polish pass — README wording, experiment_log structure + honest retrospective, LaTeX micro-style

chore: codebase hygiene pass — untrack weights, migrate to logging, tidy comments

docs: clean up R3/R4 record and consolidate technical narrative

docs: finalize R4 documentation — Dueling 84% Holdout, full ablation record

feat(round4): four-algorithm ablation — Dueling best at 84% Holdout

docs(round4): finalize R4 Double DQN results — 78% Holdout, Grid-SPL clarification

docs(round4): complete experiment record — A1/A2/A3 full EVAL data and conclusions

feat(round4): upgrade obs 3->4 channels (visited_map) + EVAL-based checkpoint

feat(round3): buffer=80k + target_freq=1500 + shaping=0.5 → 74% holdout, SPL=0.735

feat(round2): extended training, Double DQN 64% holdout, SPL=0.633

feat(round1): baseline DQN variants — Vanilla/Double/Dueling/Double+Dueling