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/0749-modules-namespaced-only-bare-param-alias-not-visible.sx

@@ -0,0 +1,17 @@
+// Bare PARAMETERIZED-struct alias visibility under a NAMESPACED-only import —
+// the generic-struct sibling of 0747 (plain alias) and 0743 (named type). A
+// generic-struct instantiation alias (`Secret :: Box(i32)`) registers ONLY a
+// named struct type in the TypeTable; its raw import fact stays `.const_decl`,
+// so before the fix it was NOT recognised as a type author and a BARE `Secret`
+// leaked to the registered struct with NO diagnostic (the value silently came
+// out 42). The unified declaration-fact writer routes the instantiation alias
+// through `type_aliases_by_source`, so the bare-TYPE gate treats it like any
+// other alias: `dep.sx` is imported only as `dep :: #import`, so bare `Secret`
+// is reachable ONLY as `dep.Secret` and must NOT resolve. Regression
+// (attempt-5 R4-parameterized-alias-leak).
+dep :: #import "0749-modules-namespaced-only-bare-param-alias-not-visible/dep.sx";
+
+main :: () -> i32 {
+    s : Secret = .{ value = 42 };
+    s.value
+}