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/0830-modules-flat-ns-same-name-forward-alias.sx

@@ -0,0 +1,16 @@
+// A flat import and a namespaced import both exporting `B :: u8` must not
+// preempt the own module's `A :: B; B :: u64;` forward alias chain.
+// Regression: issue 0107 — flat B :: u8 was winning before own B :: u64
+// was processed.
+
+std :: #import "modules/std.sx";
+#import "0830-modules-flat-ns-same-name-forward-alias/flat.sx";
+ns :: #import "0830-modules-flat-ns-same-name-forward-alias/ns.sx";
+A :: B;
+B :: u64;
+
+main :: () -> i32 {
+    x : A = 300;
+    std.print("{}\n", x);
+    0
+}