Support Quoted-Printable

[dipu-bd]

Add a Quoted-Printable codec (email/MIME). Niche for this audience but a recognized gap versus general-purpose codec libraries.

Architecture fit

• Stateful line-folding (76-char soft limit, = soft line breaks) tensions with the whole-buffer design — call this out; the encoder must track column position. Decoder is simpler (reverse the escapes, drop soft breaks).
• Standalone logic; does not use the bit engine.

Differential oracle: no dev-dep oracle in-tree — vendor RFC 2045 examples; a reference impl, if added, belongs under dev_dependencies only (owner sign-off, per the zero-dependency invariant).

Spec: RFC 2045 §6.7

Effort: M

Checklist

• Encoder with soft line-break column tracking
• Decoder handling soft breaks + =XX escapes
• Known-answer vectors from RFC 2045; invalid-input group
• README / CHANGELOG / example / test_integration updated
• Format / analyze / test (vm + node) green