v1.0.1

Correctness and packaging fixes found after the 1.0.0 release. No API changes,
but weighted BetweennessCentrality now rejects input it previously accepted —
see below.

Fixed

• Weighted BetweennessCentrality silently returned wrong scores when any edge
  weight was zero, and now throws NegativeWeightException instead. Brandes'
  path counting requires every vertex to settle after its shortest-path
  predecessors; a zero-weight edge ties the two at equal distance, so the settle
  order could invert them and drop shortest paths from the counts. Affected all
  three weighted overloads. Strictly positive weights were, and remain, correct;
  the hop-count overloads were never affected. Support for zero-weight edges is
  planned for a future release.
• ToMermaid now escapes # as #35; in vertex and edge labels. Mermaid reads
  # as the start of an entity escape, so a label containing one rendered as
  different text — and the literal label #quot; was indistinguishable from a
  label holding a real quote.
• The NuGet.org package readme now renders the logo: the image is a Markdown
  reference (NuGet strips the bare <img> HTML) and the package ships a
  dedicated icon.png rather than reusing logo.png.
• The documentation site shows the Graph1x logo in the navbar instead of the
  default DocFX logo.

Changed

• Both READMEs gained CI and coverage badges and a "How this was built"
  disclosure; CI now publishes coverage to Codecov.