Replace the old approach of linking verbose_air.zig (and the full Zig
compiler internals) into the test binary with a build-time generator
(verbose_air_gen.zig) that pre-computes AIR data for corpus files.
The generator runs as a build step, compiling each corpus file through
the Zig compiler and serializing the resulting AIR to binary files.
It produces air_data.zig and tag_names.zig bridge files that the test
binary imports as anonymous modules. This removes the heavyweight
zig_compile_air extern dependency from the test binary.
Key changes:
- build.zig: add air_gen executable build+run step, anonymous imports
- verbose_air_gen.zig (new): build-time AIR generator with symlink
workaround to avoid lib/std/ module path conflicts
- corpus.zig (new): centralized corpus file list with num_passing
- sema_test.zig: replace zig_compile_air extern with parsePrecomputedAir
- stages_test.zig: use corpus.zig and @import("air_data")
- sema.c: zero dead block data in comptime switch handler so the
dead-block skip rule fires correctly with precomputed data
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>