Model build.zig.zon package dependencies for replacement parity

Problem

Azazel records package intent today, but replacement parity requires richer build.zig.zon modeling.

Needed

• Parse/record dependency names, URLs, hashes, paths, lazy flags, and package modules.
• Preserve dependency aliases used by module imports.
• Distinguish dependency-fetch failures from package-format failures.
• Support dependency cache roots in reproducible runner output.

Corpus drivers

• ZLS uses multiple package dependencies and generated version data.
• MicroZig hits dependency zip handling.
• Capy exposes transitive package-format drift.
• zig-gamedev has a large dependency graph that now builds on 0.15.2.

Done when

• Corpus manifests include enough dependency metadata to explain missing/failing deps without reading upstream build scripts manually.
• --build classifications remain stable across fresh clone roots.
• A first Azazel target slice can import a build.zig.zon dependency module.

Start by examining the existing build.zig.zon handling and the corpus manifests, then run the --build classifications across fresh clone roots. Trace how dependency names, URLs, hashes, paths, lazy flags, aliases, modules, and cache roots are represented. Done means manifests explain dependency failures, classifications remain stable, and an Azazel target slice can import a build.zig.zon dependency module.