v0.6.1

feat: bump to rpic 0.6.1 and adopt the new core surface (#6)

- rpic-core/rpic-render 0.1.0 -> 0.6.1 (crates.io); package version
  aligned at 0.6.1.
- CompileOptions instead of prepending the circuit library: with
  circuits = TRUE, error positions stay relative to the user's source
  (rpic-lang#181).
- texlabels argument on rpic_svg/rpic_png/rpic_pdf/rpic_manifest and as
  a knitr chunk option; the RaTeX math renderer is now registered (it
  never was — texlabels would have fallen back to literal text).
- Structured errors: compile failures raise a classed rpic_error
  condition with the diagnostic on e$info (message/line/col/end_col/
  file/kind/found/expected/hint; NA = absent), via the new
  rpic_core::compile_with_diagnostics.
- rpic_manifest now documents the {warnings} field of the bundle.
- Wrappers/roxygen docs regenerated; README updated.

Closes #5

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>