fix: enforce sized integer runtime bounds

[vycdev2]

Summary

• enforce declared runtime ranges for int8/int16/int32 and uint8/uint16/uint32 after checked expressions and at typed interpreter boundaries
• resolve primitive aliases before runtime normalization and report deterministic type-and-range diagnostics
• add unit and end-to-end regression coverage for variable arithmetic, assignment, parameter, return, and nested-expression contexts
• document the tree-walking interpreter contract in the design and architecture notes

Verification

• cargo build — passed
• cargo test -q — passed
• cargo fmt --check — passed
• cargo run -q -p jett_cli -- format --check tests/runtime_fail/<fixture>.jett (all six fixtures) — passed
• git diff --check — passed

Risk

• Low: the change is limited to interpreter normalization for fixed-width primitive integer carriers; full-range uint64 behavior remains on its existing path.

Closes #10

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.

[vycdev]

Two runtime paths still miss the acceptance criteria:

1. secret[T] preserves the underlying numeric type in the typechecker, but normalization only recognizes a bare primitive or an alias. A checked expression is recorded as secret[uint8], while typed-boundary type_expr_name collapses the generic to secret, so secret[uint8] maximum = 255; secret[uint8] one = 1; secret[uint8] overflow = maximum + one reaches 256 without this range check. Please unwrap the secret qualifier (including aliases whose base is secret-wrapped) and add an end-to-end regression.

2. uint32 still uses Value::Int64, and eval_binary_op performs checked i64 arithmetic before expression normalization. For example, 4294967295 * 4294967295 fails as integer overflow: ... before normalize_sized_integer runs. Issue #10 explicitly requires deterministic diagnostics identifying the affected primitive type and operation or boundary. Please cover this path with a uint32 multiplication regression and retain uint32 in the diagnostic.

I could not run the Rust suite in this review environment because Cargo is unavailable; these findings follow directly from the type-name and evaluation paths.

[vycdev]

This only resolves aliases to a bare name. It never unwraps secret[...]: checked expression metadata uses names such as secret[uint8], and type_expr_name returns just secret for a generic type at typed boundaries. Consequently secret-tainted sized arithmetic can still escape its underlying primitive range. Please normalize through the secret qualifier and test an overflowing secret[uint8] expression.

[vycdev2]

Addressed the requested runtime paths in commit 9e3eca5:

• unwrap secret[T] and aliases whose base is secret-wrapped before fixed-width normalization;
• retain the checked uint32 type, operation, and range when host i64 multiplication overflows;
• add end-to-end regressions for direct/aliased secret[uint8] overflow and uint32 multiplication overflow.

Verification:

• cargo build — passed
• cargo test -q — passed
• cargo fmt --check — passed
• Jett formatter checks for all three new fixtures — passed
• git diff --check — passed

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.