feat(western): fix Koch house trisection and add Swiss house goldens

[Jowitt13]

What changed

• Corrected the Western Koch house trisection: cusps now use the MC degree's semi-diurnal arc and shifted ascendants.
• Added an offline, independent Swiss Ephemeris swetest golden fixture for Placidus, Koch, Porphyry, Equal, and Whole-sign houses.
• Added fail-closed capture tooling, strict swetest output parsing, fixture provenance hashes, and high-latitude no-fallback checks.
• Documented each per-system golden tolerance, measured maximum deviation, and exact margin.

Why

Independent synthetic-reference checks exposed a material Koch deviation in the prior implementation. The corrected implementation is validated against five synthetic technical epochs; no real birth data or external binary is included in the repository.

Validation

• 675 tests / 33 files
• pnpm run verify:cloud
• pnpm run build twice with no output drift
• fixture provenance cross-check: 25 reference calls and 52 raw-stream SHA-256 entries

Boundaries

• No Release, tag, published asset, dependency-lock, or personal-data change.
• The Swiss binary and raw capture remain outside the tracked repository.
• This is a draft pending CI and human review.