Wave B adds six pure-gemmology tools and upgrades, all reusing the
existing component patterns and mineral database:

* B1 — Pleochroism Reasoner (/tools/optical): observed colour count and
  colours rank candidate species and explain isotropic/uniaxial/biaxial
  systems.
* B2 — Hanneman/Hodgkinson short-cut RI (/tools/measurement): contact-
  liquid relief observations bracket the RI band of over-the-limit and
  rough stones, then filter the database to candidate species.
* B3 — GIA-style cut-grade overlay on ProportionAnalyzer for diamond
  round-brilliants: per-parameter grades plus a "limiting parameter"
  callout.
* B4 — Carat Estimator: girdle-thickness multiplicative correction
  (1.00–1.12) on the L×W×D×SG×factor estimate.
* B5 — RI Lookup: optional double-reading mode infers birefringence and
  optic character (SR/DR) and looks up gems by the average RI.
* B6 — SG Calculator: water-temperature correction using a NIST-derived
  ρ_water interpolation table.

All new pure logic ships with vitest coverage; full suite is green
(245/245), production build passes (912 pages).

…reasoner

Adds four new gemmological reasoning widgets backed by pure-TypeScript
parsers and reference tables, avoiding a multi-day Python schema
migration on the mineral-database package. The same data can later be
populated into SQL columns without breaking these widgets.

C1 — UV fluorescence lookup (`/tools/lab`): parses the freeform
`fluorescence` field for LWUV / SWUV / phosphorescence and ranks
candidates by colour and intensity. Surfaces a treatment red flag for
chalky SWUV in corundum (heat-treatment indicator).

C2 — Spectroscope band-matcher (`/tools/lab`): inverse to the
display-only SpectroscopeCalculator. User ticks observed absorption
lines on a colour-coded wavelength scale; widget ranks 16 species from
a curated reference table (chrome doublet, didymium, almandine 504/527,
zircon U-line, peridot triplet, cape diamond N3, etc.). Selective
(diagnostic) bands dominate the ranking.

C3 — Treatment-detection wizard (`/tools/advanced`): pick the gem kind,
tick observed clues (silk halos, chalky SWUV, flash effect, surface
bubbles, residue, jadeite acid-etch, HPHT decolourisation, …); evidence
weighting produces a ranked likelihood per treatment with positive and
negative supporting clues.

C4 — Optic-sign / 2V reasoner (`/tools/optical`): user enters polariscope
result + ω/ε (uniaxial) or α/β/γ (biaxial); widget computes optic sign,
birefringence, and 2V via Mallard's formula, then ranks species whose
parsed `optical_character` matches the observation.

All four ship with vitest coverage of their pure matchers (parsers,
sign rules, scoring functions). 288/288 tests pass; build green.