Add source-backed Graphcal feature stress projects

[shunichironomura]

Summary

• add four reference-backed projects selected for Graphcal feature coverage rather than formula count
• reproduce certified or explicitly published outputs from NIST, DOE, USNO, and FAO
• document each source-to-assertion mapping and identify extra feature-only outputs that are not treated as oracles

Feature coverage

Project	Newly exercised corpus surface
NIST load-cell fit	Fin and coordinate axes, multi-declarations, key conditionals, dense linear algebra, assertions/assumptions, layered plots
DOE impedance	custom electrical dimensions/units, dimension-aware complex arithmetic, required dimension ports, reusable DAG instances
USNO J2000	constrained Datetime<S>, TT/TAI/UTC conversions, datetime arithmetic/equality, integer extractors
FAO soil-water balance	algebraic records, exhaustive match, heterogeneous scan, Bool, Int, if, argmin, typed keys, plotted boolean channel

Validation

• ruff check .
• ruff format --check .
• uv run -m pytest (39 passed)
• uv run validate-corpus
• uv run test-graphcal ../graphcal/target/release/graphcal (15/15 passed)
• rendered and validated NIST layered plot JSON and FAO line-plot JSON

Provenance and privacy

All manifest expectations are values explicitly certified or reported by the cited public sources. Additional computed nodes exist only to exercise Graphcal features and are labeled as non-reference outputs in the evidence records. No private project material is included.