General bug fixes

[metafates]

This PR fixes several different bugs.

I've used Claude Fable 5 with ultracode effort to find and reproduce these bugs. Same model partially assisted in fixing them. After that, I thoroughly validated and corrected results.

Bugs fixed:

• Panics in tests now record the actual recovered value, are observed by after-hooks as a failed test.
• t.Setenv and t.Chdir now enforce the standard library's conflict guards against t.Parallel.
• Plugin hooks and overrides with equal priority now run deterministically, in the declaration order of plugins.
• Overrides are now applied in the documented priority order, consistent with hooks.
• t.Error called after t.Fatal (e.g. from a cleanup) no longer downgrades the recorded fatal failure kind.
• Annotations no longer leak between instantiations of a generic suite.
• Persistent cache reads no longer follow a symlink swapped in after validation.
• The error for a non-pointer exported field now names the owning type and field.