D030 - The two halves check each other where material is unavailable

Elf::tables's current-convention branch was written from reasoning and had never been executed against anything - every module this repository has been pointed at is previous-generation. Code that has never run is the defect class this project keeps finding in other people's work, and shipping one was not defensible.

It cannot be fixed with material nobody has. It can be fixed with the other half of the crate: dynlib can write a current-convention module, so the reader can be made to read one. tests/current.rs builds the same linked object under both conventions and asserts that every tag number differs and every import that comes back out is identical.

That is a real check with a stated limit, and both parts matter. It proves the writer and the reader agree about the tag numbers, the virtual-address origin, the mapped segment and the rebasing. It proves nothing about what a console accepts. The doc comment says so, so the limit travels with the capability rather than living only here.

The same test also pins the one row in data/library-versions.tsv end to end: the display library is declared 0.0 on the previous generation and 1.1 on the current one, read back out of a built module rather than out of the function that decides it.