fix: use getAllInterfaceFields in control-flow.ts for inherited fields

[cs01]

Summary

• PR fix: use getAllInterfaceFields to include inherited fields in interface codegen #114 fixed getAllInterfaceFields usage in member.ts, variable-allocator.ts, interface-allocator.ts, class.ts, and llvm-generator.ts — but missed control-flow.ts
• control-flow.ts had 13 sites using direct .fields access on interface objects, missing inherited fields from extends clauses
• This caused wrong GEP indices and missing metadata for for-of loops, chained member access, union type narrowing, and type guards on interfaces with inheritance
• Fixed all 13 sites to use this.ctx.getAllInterfaceFields() instead

Test plan

• All 428 tests pass (includes existing interface-extends fixture + new interface-extends-for-of)
• New fixture interface-extends-for-of.ts exercises for-of over an array of objects with an inherited interface

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