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/protocols/expected/0415-protocols-protocols.stdout

@@ -0,0 +1,27 @@
+=== Protocols ===
+P1.1: 3
+P1.2: 30
+P2.1: 42
+P2.2: 150
+P2.3: 5 10
+P3.1: 5
+P3.2: 12
+hi hi 
+P4.1: 2
+yo yo 
+P4.2: 2
+P4.3: 6 2
+P5.1: true false
+P5.2: 10 20
+P5.5: true false
+P5.3: true false
+P6.1: true false
+P6.2: true false
+P6.3: true false
+P6.4: 40
+P6.5: 20
+P7.1: 30
+P7.2: 10 300
+P2.6: 5 10
+P2.7: 15
+P3.3: 102