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/optionals/expected/0900-optionals-optionals.exit

@@ -0,0 +1 @@
+0

examples/optionals/expected/0900-optionals-optionals.stderr

@@ -0,0 +1 @@
+

examples/optionals/expected/0900-optionals-optionals.stdout

@@ -0,0 +1,20 @@
+x = 42
+y = null
+x! = 42
+x ?? 0 = 42
+y ?? 99 = 99
+if-bind x: 42
+if-bind y: none
+match some: 42
+match none: 0
+p?.value = 10
+q?.value = 0
+o1.inner?.val = 99
+o2.inner?.val = 0
+narrowed a: 10
+guard 42: 42
+guard null: 0
+both: 10 20
+guard2: 7
+default next: null
+comptime: 141

examples/optionals/expected/0901-optionals-match-optional-arms.exit

@@ -0,0 +1 @@
+0

examples/optionals/expected/0901-optionals-match-optional-arms.stderr

@@ -0,0 +1 @@
+

examples/optionals/expected/0901-optionals-match-optional-arms.stdout

@@ -0,0 +1,6 @@
+ok: floating is null
+ok: left h=.leading
+ok: center h=.center
+ok: top_right h=.trailing v=.top
+rect
+text

examples/optionals/expected/0902-optionals-optional-all-null.exit

@@ -0,0 +1 @@
+0

examples/optionals/expected/0902-optionals-optional-all-null.stderr

@@ -0,0 +1 @@
+

examples/optionals/expected/0902-optionals-optional-all-null.stdout

@@ -0,0 +1,3 @@
+r1 = 150.000000
+r2 = 150.000000
+r3 = 200.000000

examples/optionals/expected/0903-optionals-optional-roundtrip.exit

@@ -0,0 +1 @@
+0

examples/optionals/expected/0903-optionals-optional-roundtrip.stderr

@@ -0,0 +1 @@
+

examples/optionals/expected/0903-optionals-optional-roundtrip.stdout

@@ -0,0 +1,10 @@
+=== Direct calls ===
+d1 = 150.000000
+d2 = 150.000000
+d3 = 200.000000
+d4 = 110.000000
+=== Protocol dispatch ===
+r1 = 150.000000
+r2 = 150.000000
+r3 = 200.000000
+r4 = 110.000000

examples/optionals/expected/0904-optionals-any-to-string-optional.exit

@@ -0,0 +1 @@
+0

examples/optionals/expected/0904-optionals-any-to-string-optional.stderr

@@ -0,0 +1 @@
+

examples/optionals/expected/0904-optionals-any-to-string-optional.stdout

@@ -0,0 +1,2 @@
+S{a: 42, b: hi, c: true}
+S{a: null, b: null, c: null}

examples/optionals/expected/0905-optionals-unwrap-field-chain.exit

@@ -0,0 +1 @@
+0

examples/optionals/expected/0905-optionals-unwrap-field-chain.stderr

@@ -0,0 +1 @@
+

examples/optionals/expected/0905-optionals-unwrap-field-chain.stdout

@@ -0,0 +1,10 @@
+chain id:  hello
+chain n:   42
+bind id:   hello
+bind n:    42
+meth ptr:  hello
+meth val:  50
+nest tag:  deep
+nest k:    7
+index 0:   10
+index 2:   30