feat(dashboard): add academic-year assessment context

[grant-mccurdy]

Summary

• replace generic assignment labels with seven paired BOY/EOY academic-year windows while retaining raw source labels
• add explicit synthetic assessment context and course-specific proficiency references
• regenerate and verify the dashboard publication manifest

Portfolio impact

Assessment Analytics now reads like an actual longitudinal assessment product without implying that synthetic demonstration thresholds are institutional policy.

Validation

• make check
• make privacy-check (0 failures; one expected small-synthetic-group warning)
• dashboard publication: 4,018 synthetic student-period records, checksum verified
• git diff --check

Public readiness

The output remains entirely synthetic. Raw assignment labels are preserved as lineage metadata, benchmark methods are explicitly illustrative, and privacy validation found no emails, tokens, private paths, Canvas references, or real identifiers.

[grant-mccurdy]

Reviewed the exact builder and manifest patch with the passing publication check. Academic-year/window metadata preserves raw source labels, course references are explicitly synthetic and bounded, the published checksum verifies, and privacy validation reports zero failures.