fix: strict type resolution — eliminate silent default-to-double/i8*

[cs01]

Summary

• Replace silent return "double" defaults in fieldToLlvmType() (class.ts) with explicit throw Error — null fields and unrecognized types no longer silently become numbers
• Replace silent return "double" in getScopeVarType() (closure-analyzer.ts) — missing closure variables now error
• Add explicit handling in canonicalTypeToLlvm() for any, never, void, object, function types (=>), inline object types ({...}), already-resolved LLVM types, and uppercase class/interface names
• Fix LLVM-type-as-tsType bug in member.ts:1719 — was passing "i8*" LLVM type to a TS→LLVM conversion function
• Fix for...of on string codegen bug — ChadScript treats string char iteration as double array, use index loop instead

Native compiler corruption discovery

• The old catch-all return "i8*" in canonicalTypeToLlvm was silently masking 294 corrupted type strings per Stage 1 build
• Root cause identified: 93 inline as { name: string; type: string } assertions on InterfaceField elements across 17 codegen files
• The native compiler can't determine struct layout from anonymous assertions, falls back to csyyjson_obj_get which reads garbage memory
• Fix: replace all inline assertions with named InterfaceField type from ast/types.ts (separate PR)
• Catch-all return "i8*" kept for now with clear TODO comment documenting root cause

Test plan

• 437 tests pass
• verify:quick passes (tsc + Stage 0 + Stage 1)
• macOS CI passes