Fix parsing of as/satisfies between ** operators

[magic-akari]

Follow-up to #4192.

Accounts for ** being right-associative when rejecting as/satisfies expressions that cannot be safely erased. Adds regression coverage for direct and chained forms.

• Close: as/satisfies between exponentiation operators cannot be safely erased TypeScript#63661

[Copilot]

Pull request overview

Fixes unsafe erasure of as and satisfies between right-associative exponentiation operators.

Changes:

• Centralizes binary-operator consumption logic.
• Handles equal-precedence ** operators correctly.
• Adds direct and chained regression coverage.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/parser/parser.go	Accounts for exponentiation associativity during parsing.
testdata/tests/cases/compiler/disallowUnerasableAssertion.ts	Adds regression cases.
testdata/baselines/reference/compiler/disallowUnerasableAssertion.errors.txt	Captures expected diagnostics.
testdata/baselines/reference/compiler/disallowUnerasableAssertion.js	Captures JavaScript emit.
testdata/baselines/reference/compiler/disallowUnerasableAssertion.symbols	Updates symbol baselines.
testdata/baselines/reference/compiler/disallowUnerasableAssertion.types	Updates type baselines.