Bump to 9.12.2

[pe200012]

Resolves #8. Closes #6.

Also fixed the extraneous space in Operator.test

[Copilot]

Pull request overview

This PR adds support for GHC 9.12.2 to the retrie library. The changes involve updating dependency version bounds and adding extensive conditional compilation (CPP) guards to handle API differences between GHC versions.

Changes:

• Updated GHC and dependency version bounds in retrie.cabal to support GHC 9.12.2
• Added CPP guards throughout the codebase to handle GHC 9.12+ API changes (Fixity, Match, Pattern, Lambda, Token/annotation APIs)
• Updated CI configuration to test against GHC 9.12.2

Reviewed changes

Copilot reviewed 15 out of 16 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
retrie.cabal	Updated dependency version bounds for GHC 9.12.2 support; added GHC 9.12.2 to tested-with; removed trailing space from copyright field
.github/workflows/ci.yml	Added GHC 9.12.2 to test matrix with fail-fast: false
CHANGELOG.md	Added entry for GHC 9.12 support
.gitignore	Added .stack-work/ directory
hse/Fixity.hs	Added CPP guards for Fixity constructor changes (removed SourceText parameter in 9.12+)
Retrie/Subst.hs	Added CPP guards for transferEntryDP return type and HsMatchContext signature changes
Retrie/Rewrites/Patterns.hs	Added CPP guards for HsRecFields, pattern annotation, and mkMatch API changes
Retrie/Rewrites/Function.hs	Added CPP guards for m_pats accessor, pattern matching, and operator application changes
Retrie/Replace.hs	Changed transferAnchor to transferEpAnn function name
Retrie/PatternMap/Instances.hs	Added extensive CPP guards for literal patterns, lambda variants, expression patterns, pattern constructors, type variable binders, record fields, statement types, and ValBinds representation changes
Retrie/GHC.hs	Added CPP guards for type variable binder extraction with different APIs for 9.12+
Retrie/Fixity.hs	Added CPP guards for Fixity pretty-printing (removed SourceText parameter)
Retrie/Expr.hs	Added extensive CPP guards for anchor handling, location construction, lambda construction with new HsLamVariant, let expressions, applications, type variables, pattern construction, pattern-to-expression conversion, precedence, and parenthesization
Retrie/ExactPrint/Annotated.hs	Added CPP guards for setEntryDPA signature (removed Default constraint for 9.12+)
Retrie/ExactPrint.hs	Added CPP guards and Monoid/Semigroup/Default instances for GHC 9.12 annotation types; updated functions for anchor/annotation transfer, comment handling, and entry delta position handling
Retrie/Context.hs	Added CPP guards for context updates handling Fixity without SourceText and HsLet parameter changes

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