Sema is the compiler stage after AstGen that produces AIR (Analyzed Intermediate Representation) from ZIR, performing both type analysis and comptime evaluation.
AIR is fully typed, generated per-function, and consists of instructions, extra data, and a values array for comptime-known constants.
Key data structures include Value (comptime values), Type (comptime types), and TypedValue (value paired with its exact type).
The core function analyzeBodyInner loops over ZIR instructions, mapping each to zero or more AIR instructions using the inst_map.