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/basic/0017-basic-conditions.sx

@@ -0,0 +1,18 @@
+#import "modules/std.sx";
+
+main :: () {
+    x:= 32;
+    y:= 40;
+
+    if 0 <= x <= 100 and 0 <= y <= 100 {
+        print("contained");
+    }
+
+    if 1000 > x > -100 and 0 <= y <= 100 {
+        print("contained");
+    }
+
+    if 1000 > x >= -100 and 0 <= y <= 100 {
+        print("contained");
+    }
+}