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/0774-modules-bare-generic-head-visible-author/b.sx

@@ -0,0 +1,11 @@
+// The bare-VISIBLE author: a one-field generic `Box` (size 8). `b.sx` itself
+// flat-imports `c.sx`, so `b_make`'s `Box(i64)` resolves here (the head is one
+// flat hop away in this module) — but a file that imports b.sx reaches `c.Box`
+// only at two hops, so it must NOT win the bare head in the importer.
+Box :: struct($T: Type) { x: T; }
+
+#import "c.sx";
+
+b_make :: () -> Box(i64) {
+    .{ x = 99 }
+}

examples/modules/0774-modules-bare-generic-head-visible-author/c.sx

@@ -0,0 +1,5 @@
+// The NON-visible 2-flat-hop author: a two-field generic `Box` (size 16). Same
+// template NAME as b's, different layout. It wins the global last-wins
+// `struct_template_map`, so the bare head in a file importing only b.sx must NOT
+// pick it.
+Box :: struct($T: Type) { x: T; y: T; }