test: group examples into per-category folders

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.

examples/modules/0720-modules-qualified-own-import/calc.sx

@@ -0,0 +1,8 @@
+// `calc` is pulled in under a QUALIFIED namespace by the consumer
+// (`calc :: #import …`), yet its own body calls `triple` / `base` from
+// calc.sx's OWN flat `#import "util.sx"`. The qualified alias `calc.compute`
+// must lower in calc.sx's source context so those own-import callees stay
+// visible — issue 0100 F1.
+#import "util.sx";
+
+compute :: () -> i64 { return triple(base()); }

examples/modules/0720-modules-qualified-own-import/util.sx

@@ -0,0 +1,2 @@
+triple :: (x: i64) -> i64 { return x * 3; }
+base   :: () -> i64 { return 14; }