fix: remove function aliases from grader_api, classes only, NaN protection

fix: grader classes with grade() method per Meta feedback

fix: grader handles all call patterns, reset reward 0.01

fix: class-based graders with grade() method per Meta instructions

fix: bulletproof graders - never throw, always return float in range

fix: grader_api returns float only, not tuple

fix: resolve merge conflict in grader_api.py

Update grader_api.py

CRITICAL FIX: Add missing grader_api.py

Add comprehensive instrumentation to all graders for validator diagnostic

Add detailed instrumentation to grade_task1 and normalize_reward for validator debugging

CRITICAL FIX: Graders now return FLOAT ONLY (not tuples) for validator contract compliance - extracted float from raw grader tuples

CRITICAL FIX: Wrappers now return full tuples (reward, error, bugs) instead of just floats - fixes env.py unpacking

FINAL FIX: Centralized universal reward normalization - GUARANTEES all scores in (0.01, 0.99)

Add validator invocation logging to all grader wrappers

Phase 2: Benchmark Quality Upgrades - Progressive graders, realistic multi-bug tasks, ground_truth exposure