[Feature] Context-aware safe integer casts

[pabloosabaterr]

Description

Integer casts currently warn about possible precision loss even when the value is provably safe from surrounding conditions.

Warnings should be suppressed when the value range is known to be safe.

Example

a: i8 := ... 

if a >= 0 {
    // a ∈ [0, I8_MAX]

    b: u8 := a as u8   // should NOT warn 
}

c: u8 := a as u8       // should warn

Rule

A cast is safe if:

range(source) ⊆ range(target)

Benefit

• Removes false precision-loss warnings
• Improves static analysis