fix(reward): extract boxed answer in RLPR WebInstruct math grading (#170)

[galuis116]

Closes #170

Summary

_check_rlpr_webinstruct in src/trinity/orchestration/reward.py grades WebInstruct-verified RLPR items. For a math answer it fed the raw candidate text into math_equal / normalize_math_answer without first extracting the answer — unlike _check_math, which uses extract_boxed / extract_last_number. Since normalize_math_answer does not strip \boxed{...}, a correct boxed answer (the format format_hint("rlpr") tells the worker to use) scored 0.

score_text("rlpr", r"The area is \boxed{15}.", {"ground_truth":"15","source":"WebInstruct-verified-val_Avg2"})
# -> 0.0 (should be 1.0); the same answer under math500 -> 1.0

What Changed

• src/trinity/orchestration/reward.py: extract the answer before the math compare — cand_math = extract_boxed(cand) or extract_last_number(cand) or cand, gold_math = extract_boxed(gold) or gold — mirroring _check_math.
• tests/test_rlpr_webinstruct_math.py (new, offline): boxed answer scores 1.0, plain number still works, wrong boxed scores 0, the letter path is unchanged, and RLPR agrees with the math path on a boxed answer.
• docs/JOURNAL.md: entry per repository protocol.

Why This Matters

Every WebInstruct-verified RLPR math item answered in the requested \boxed{...} format was a false negative, understating accuracy and corrupting the reward signal for those items. Verified offline: the new tests fail on the old code and pass on the fix; 47 existing rlpr/reward tests still pass.

Notes

• Distinct from reward: MMLU-Pro (RLPR) answers E–J always score 0 — choice grading is capped at A–D #116 / RLPR MMLU-Pro is scored as 4-option (A–D), so any correct answer in E–J is always marked wrong #122 (RLPR MMLU-Pro choice grading, letters E–J) — this is the WebInstruct math path.
• This PR was repurposed from an earlier agreement-diagnostic branch; the pivot is visible in history.

[galuis116]

Note: I've repurposed this PR onto a distinct, self-contained fix — RLPR WebInstruct math grading now extracts \boxed{} answers (Closes #170). The force-push above swaps the contents; the agreement-diagnostic work can be reopened separately if wanted.