Move examples/*.sx and their expected/ snapshots into per-category
subfolders (examples/<category>/...). Folder = leading filename token,
with ffi-objc/ffi-jni kept whole; filenames are unchanged. The corpus
runner and LSP sweep now discover each category's expected/ dir, while
issues/ stays flat. Example 1058's repo-root-relative companion import
is made file-relative. Path strings embedded in 164 snapshots were
regenerated (path-only changes). Test-layout docs in CLAUDE.md updated.
Eliminates the recurring -Dupdate-goldens churn: these 5 were 0-byte
outliers while 484 other empty goldens use the writeGolden-produced
1-byte "\n" form. The corpus runner trims trailing newlines on both
sides during verify, so both forms passed — but regen always rewrote
them to 1-byte. Conforming them makes -Dupdate-goldens idempotent.
