[bug] MATH grader: NBSP / middle-dot thousands (1 000 / 1·000) extract as "000"

[marktech0813]

Problem

Non-breaking space (U+00A0) and middle dot · (U+00B7) are common thousands separators (EU/typography). Extract keeps only the last group:

extract_last_number("1\u00a0000")  # "000"
extract_last_number("1·000")       # "000"
score_text("math500", "1\u00a0000", "1000")  # 0.0
score_text("math500", "1·000", "1000")       # 0.0

Sibling of ASCII , / ideographic ， / thin-space fixes.

Expected

Both forms extract/normalize as 1000.

Environment

• origin/main

[github-actions]

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