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/0785-modules-qualified-generic-static-missing-member/a.sx

@@ -0,0 +1,9 @@
+// Namespace A authors only `Other` — NO `Box`. The qualified static head
+// `a.Box(i64).make(..)` must diagnose the missing member, not fall to b's `Box`.
+Other :: struct($T: Type) {
+    v: T;
+
+    make :: (value: T) -> Other(T) {
+        .{ v = value }
+    }
+}