feat(slang): complete operator emission

[hedgar2017]

Completes operator emission on the Slang frontend:

• Comparison reconciles mixed operand types to the wider integer operand, or the widest fixed-bytes width.
• Shift and exponentiation keep their right operand at its own type.
• Bitwise, shift, and negation operators apply directly to fixed-bytes values.

[Copilot]

Pull request overview

This PR completes several operator-emission behaviors in the Slang frontend by refining operand coercion rules (notably for comparisons, shifts, exponentiation, and fixed-bytes bitwise ops) and extending the MLIR layer to properly detect and reconcile fixed-bytes types during coercion and comparisons.

Changes:

• Introduces FunctionScope::coerced() and applies it broadly to simplify/standardize “emit then coerce” call sites.
• Updates shift/exponentiation and compound-assignment lowering to keep the RHS operand at its original type (instead of coercing both operands to the result type).
• Extends MLIR type/value utilities with fixed-bytes inspection and comparison reconciliation logic, and adds/updates lit tests covering fixed-bytes bitwise/shift and mixed-width integer comparisons.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
solx-slang/src/contract/function/statement/variable_declaration.rs	Uses the new coerced() helper for initializer coercion.
solx-slang/src/contract/function/expression/unary.rs	Refactors unary operator lowering to use coerced() consistently.
solx-slang/src/contract/function/expression/mod.rs	Adds FunctionScope::coerced() and refactors coerced_operands() to use it.
solx-slang/src/contract/function/expression/call/mod.rs	Switches call argument coercions to coerced() for consistency.
solx-slang/src/contract/function/expression/call/arguments.rs	Uses coerced() for parameter/argument coercion.
solx-slang/src/contract/function/expression/bitwise.rs	Adjusts shift lowering so shift amounts keep their own type.
solx-slang/src/contract/function/expression/assignment.rs	Keeps RHS type for shift compound assignments; coerces RHS for other compound ops.
solx-slang/src/contract/function/expression/array.rs	Uses coerced() for array literal element coercion.
solx-slang/src/contract/function/expression/arithmetic.rs	Adjusts exponentiation lowering so exponent keeps its own type.
solx-mlir/tests/lit/fixed_bytes_shift.sol	Adds lit coverage for fixed-bytes shift with typed shift amounts.
solx-mlir/tests/lit/fixed_bytes_bitwise.sol	Adds lit coverage for fixed-bytes bitwise ops (~, ^).
solx-mlir/tests/lit/comparison.sol	Expands lit coverage for mixed-width integer comparisons.
solx-mlir/tests/lit/bitwise.sol	Expands lit coverage for shifts with “wide” RHS shift amounts and signed shift-right.
solx-mlir/tests/lit/arithmetic.sol	Updates arithmetic lit coverage to reflect revised operator emission (notably exp/neg cases).
solx-mlir/src/ir/value.rs	Extends coercion to route fixed-bytes coercions through bytes_cast; updates comparison reconciliation logic.
solx-mlir/src/ir/type/mod.rs	Adds fixed-bytes type predicates/accessors used by coercion and comparisons.
solx-mlir/src/ffi.rs	Exposes new fixed-bytes inspection functions via Rust FFI.
solx-mlir/sol_attr_stubs.cpp	Implements the fixed-bytes type predicate and size accessor for the Rust FFI.