fix(codegen): VIBEE emits undefined eqlPrimitive and wrong slice methods

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Scholar Finding (0.9/1.0). codegen_engine_final_upgrade.zig:207 calls eqlPrimitive() which is never defined. Fix: replace with std.mem.eql(u8, a, b). Also: GenericTypeCache.resolved and ImportTracker.stdlib_imports are []const u8 but code calls .get()/.put()/.iterator() - should be std.StringHashMap.

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Fixed in PR #544 (merged). VIBEE collection types now use std.StringHashMap.