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/diagnostics/1132-diagnostics-array-dim-non-integral-float.sx

@@ -0,0 +1,19 @@
+// A NON-integral float constant (`4.5`) used as an array dimension is a hard
+// error — only an integral float (`4.0`) folds to a count. Clean diagnostic +
+// non-zero exit, NOT a fabricated length.
+//
+// The dimension follows the unified float→int narrowing rule (F0.11 / issue
+// 0095): an integral float folds, a non-integral one is rejected as "not an
+// integer" — the SAME `floatToIntExact` judgement the typed local/field/param/
+// const sites use (the count path is the last of the five sites to unify).
+//
+// Regression (F0.4 attempt 8, Agra ruling): the integral-float rule accepts
+// `4.0` as a dimension but must keep rejecting `4.5` (it is not an integer).
+#import "modules/std.sx";
+
+N : f64 : 4.5;
+
+main :: () {
+    a : [N]i64 = ---;
+    print("unreachable: {}\n", a.len);
+}