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/0783-modules-qualified-generic-alias-instance-dispatch/b.sx

@@ -0,0 +1,12 @@
+// Author B's generic `Box` — two i64 fields (size 16) whose `tag` returns
+// `self.x + 2`. Same template NAME as A's, different layout/body; it wins the
+// global last-wins `fn_ast_map["Box.tag"]`, so the alias over `a.Box` must NOT
+// dispatch to it.
+Box :: struct($T: Type) {
+    x: T;
+    y: T;
+
+    tag :: (self: *Box) -> T {
+        self.x + 2
+    }
+}