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/0735-modules-flat-same-name-fn-value-winner/a.sx

@@ -0,0 +1,4 @@
+// a.sx authors `pick` (imported first → the first-wins name-keyed winner) but
+// its body references an undefined symbol, so lowering a.pick AT ALL is an
+// error. Nothing uses a.pick — taking b.pick as a value must not pre-lower it.
+pick :: () -> i64 { return missing_from_a(); }

examples/modules/0735-modules-flat-same-name-fn-value-winner/b.sx

@@ -0,0 +1,7 @@
+// b.sx authors its OWN `pick` (returns 2) and takes it as a function VALUE. The
+// value binds b.pick (own-author wins), never the broken winner from a.sx.
+pick :: () -> i64 { return 2; }
+from_b_value :: () -> i64 {
+    g : () -> i64 = pick;
+    return g();
+}