docs(ephapax): update STATE.scm and CHANGELOG.md for parser extensions

STATE.scm: 9 new completed items tracking all parser features added
(qualified modules, Haskell comments, linear/affine modifiers,
const_decl, named record types, arrow return syntax, region colon,
keyword word-boundary fix, Decl::Const AST variant).

CHANGELOG.md: Added and Fixed sections under [Unreleased].

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath