feat: add transplanted 1D quadrature maps, docs, tests, and QBX example

[xywei]

Summary

• Add modepy.quadrature.transplanted with transplanted 1D quadrature support:

  • map functions: identity, generic sausage_d{odd}, strip, and kte / kosloff_tal_ezer
  • dispatcher: map_trefethen_transplant
  • quadrature classes: Transplanted1DQuadrature and TransplantedLegendreGaussQuadrature

• Export transplanted quadrature classes from package init modules.

• Expand quadrature docs with dedicated transplanted sections:

  • map-by-map subsections and usage guidance
  • parameter notes (strip_rho, kte_rho, kte_alpha)
  • references for Hale–Trefethen (2008) and Kosloff–Tal-Ezer (1993)

• Add a 2D QBX comparison example:

  • examples/plot-qbx-transplanted-vs-gauss.py
  • compares Gauss, KTE, strip, sausage d5/d9 on the circle with frozen centers/targets
  • sample plot:
    

• Add transplanted quadrature tests:

  • map-name dispatch and direct-map consistency
  • strip-map endpoint rejection
  • KTE parameter validation and alias coverage
  • generic sausage degree parsing/validation

Validation

• python examples/plot-qbx-transplanted-vs-gauss.py
• pytest modepy/test/test_quadrature.py -k transplanted