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/vendor/expected/1624-vendor-sqlite-module.exit

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

examples/vendor/expected/1624-vendor-sqlite-module.stderr

@@ -0,0 +1 @@
+

examples/vendor/expected/1624-vendor-sqlite-module.stdout

@@ -0,0 +1,2 @@
+row: b 2
+vendored sqlite 3.53.2 ok

examples/vendor/expected/1625-vendor-stb-image-decode.exit

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

examples/vendor/expected/1625-vendor-stb-image-decode.stderr

@@ -0,0 +1 @@
+

examples/vendor/expected/1625-vendor-stb-image-decode.stdout

@@ -0,0 +1,2 @@
+decoded 2x2 (3 channels)
+top-left pixel: 0 0 255

examples/vendor/expected/1626-vendor-stb-truetype-metrics.exit

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

examples/vendor/expected/1626-vendor-stb-truetype-metrics.stderr

@@ -0,0 +1 @@
+

examples/vendor/expected/1626-vendor-stb-truetype-metrics.stdout

@@ -0,0 +1,4 @@
+font offset >= 0: true
+init ok: true
+scale > 0: true
+ascent > 0, descent < 0: true true

examples/vendor/expected/1627-vendor-kbts-shape-context.exit

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

examples/vendor/expected/1627-vendor-kbts-shape-context.stderr

@@ -0,0 +1 @@
+

examples/vendor/expected/1627-vendor-kbts-shape-context.stdout

@@ -0,0 +1,3 @@
+context created: true
+font pushed: true
+context destroyed