fix(haskell): don't over-rename enum cases when the enum suffix already disambiguates

[schani]

Bug

For a string enum like ["ok", "error"], the Haskell renderer produced
HealthErrorHealth | OkHealth instead of the expected ErrorHealth | OkHealth.

Root cause

Error is listed as a globally forbidden identifier in
packages/quicktype-core/src/language/Haskell/constants.ts. When
ConvenienceRenderer.makeNameForEnumCase styles the enum case name to
Error, it detects a collision with that forbidden global identifier and
picks an alternative (Health_error -> HealthError) before the
enum-name suffix (Health) is textually appended at emit time in
HaskellRenderer.emitEnumDefinition. Since the suffix is only appended
after name resolution runs, the resolver never sees the final,
already-disambiguated identifier (ErrorHealth) when checking for
forbidden-name collisions, so it picks the uglier alternative unnecessarily.
The generated code was correct and round-tripped fine — this was purely
cosmetic.

Fix

HaskellRenderer now overrides makeNameForEnumCase to fold the enum-name
suffix into the proposed name itself, via a DependencyName (the same
pattern already used elsewhere for names that depend on another name, e.g.
proposeUnionMemberName). This means forbidden-word collision checking now
sees the final, suffixed identifier (ErrorHealth) rather than the bare
case name (Error), so it no longer needlessly renames it.

Emit sites (emitEnumDefinition, the ToJSON/FromJSON instances) now use
a small enumCaseName helper: for the common case (a DependencyName that
already includes the suffix) it's used as-is; for FixedNames (explicit
user-assigned accessor names, which bypass makeNameForEnumCase) it falls
back to the previous behavior of textually appending the enum name, since
those names are user-specified and shouldn't be silently changed.

Test coverage

Added a new JSON Schema fixture:

• test/inputs/schema/haskell-enum-forbidden.schema — an object with a
  string enum ["ok", "error"], i.e. the schema from the issue.
• test/inputs/schema/haskell-enum-forbidden.1.json — a matching sample.

Round-tripping alone can't distinguish generated constructor names (both
HealthErrorHealth and ErrorHealth round-trip correctly), so
HaskellLanguage.runCommand in test/languages.ts was extended to also
grep the generated QuickType.hs for the expected ErrorHealth
constructor when running this specific sample, failing the fixture if the
old, over-renamed identifier reappears.

Verification

• npm run build passes.
• npm run test:unit passes (163 tests).
• Confirmed the exact repro from the issue now generates ErrorHealth | OkHealth instead of HealthErrorHealth | OkHealth.
• Ran the Haskell code generator against several other enum-bearing schema fixtures (enum.schema, enum-with-values.schema, enum-large.schema, optional-enum.schema, keyword-enum.schema, top-level-enum.schema, multi-type-enum.schema, cut-enum.schema) to check for regressions — all generate without error and with sensible names.
• biome check passes on the changed files.
• The full FIXTURE=schema-haskell script/test run (which compiles and executes the generated Haskell via stack) was not run locally because the Haskell toolchain (stack/ghc) is not installed in this environment; CI will validate this.

Fixes #2868

🤖 Generated with Claude Code

[schani]

Retriggering CI (no CI run was created for the latest push).