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/platform/expected/1649-platform-asm-place-output.ir

@@ -0,0 +1,25 @@
+
+; Function Attrs: nounwind
+define internal i64 @compute() #0 {
+entry:
+  %alloca = alloca i64, align 8
+  store i64 0, ptr %alloca, align 8
+  %asm = call { i64, i64 } asm sideeffect "        mov ${0}, #5\0A        mov ${1}, #37\0A", "=r,=r"()
+  %asm.out = extractvalue { i64, i64 } %asm, 0
+  %asm.out1 = extractvalue { i64, i64 } %asm, 1
+  store i64 %asm.out1, ptr %alloca, align 8
+  %allocaN = alloca i64, align 8
+  store i64 %asm.out, ptr %allocaN, align 8
+  %load = load i64, ptr %allocaN, align 8
+  %loadN = load i64, ptr %alloca, align 8
+  %add = add i64 %load, %loadN
+  ret i64 %add
+}
+
+; Function Attrs: nounwind
+define i32 @main() #0 {
+entry:
+  %call = call i64 @compute()
+  %ca.tr = trunc i64 %call to i32
+  ret i32 %ca.tr
+}