Fix array validation, length calculation, and compiler diagnostics

[someone235]

This PR fixes several compiler correctness issues involving array encoding, comparisons, and ambiguous declarations.

Bug Fixes

• Reject malformed dynamic-array entrypoint payloads whose encoded length is not divisible by the element width.

• Correct .length for derived arrays so it returns the element count instead of the encoded byte count.

// Correctly evaluates to 1 rather than 8.
require(values.slice(0, 1).length == 1);

• Validate fixed-array casts using total encoded size. Equal-size reinterpretations remain valid, while casts that would produce an invalid representation are rejected.

byte[16] bytes = byte[16](int[2]{1, 2}); // Valid
byte[2] bytes = byte[2](int[2]{1, 2});   // Rejected

• Reject ordered comparisons on non-numeric values before they produce invalid numeric operations at runtime. Equality and inequality remain supported.

require("a" < "b");   // Rejected
require("a" == "a");  // Valid

• Report a compiler error when an entrypoint parameter conflicts with a contract field instead of panicking internally.

• Reject duplicate entrypoint and helper-function names instead of silently resolving them inconsistently.