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/1624-vendor-sqlite-module.sx

@@ -0,0 +1,37 @@
+// The sx library ships SQLite: `#import "vendors/sqlite/sqlite.sx"`
+// resolves through the stdlib search paths, compiles the vendored
+// amalgamation as a `#import c` unit (cached), and the bindings just
+// work — no system dependency, no flags. Pins the vendored version
+// (an OS libsqlite3 of another version must never shadow the unit)
+// and a typed round trip.
+#import "modules/std.sx";
+sq :: #import "vendors/sqlite/sqlite.sx";
+
+main :: () -> i32 {
+    v := sq.sqlite_version();
+    if v != "3.53.2" {
+        print("unexpected sqlite version: {}\n", v);
+        return 1;
+    }
+
+    db, oe := sq.Sqlite.open(":memory:");
+    if oe { print("open failed\n"); return 1; }
+    ee := false;
+    db.exec("CREATE TABLE t (name TEXT, n INTEGER); INSERT INTO t VALUES ('a', 1), ('b', 2)") catch { ee = true; };
+    if ee { print("exec failed: {}\n", db.errmsg()); db.close(); return 1; }
+
+    st, pe := db.prepare("SELECT name, n FROM t WHERE n > ?1 ORDER BY n");
+    if pe { print("prepare failed\n"); db.close(); return 1; }
+    st.bind_int64(1, 1) catch { ee = true; };
+    rc, se := st.step();
+    serr := false;
+    if se { serr = true; }
+    if serr or ee { print("step failed\n"); st.finalize(); db.close(); return 1; }
+    if rc == sq.SQLITE_ROW {
+        print("row: {} {}\n", st.column_text(0), st.column_int64(1));
+    }
+    st.finalize();
+    db.close();
+    print("vendored sqlite {} ok\n", v);
+    0
+}

examples/vendor/1625-vendor-stb-image-decode.sx

@@ -0,0 +1,35 @@
+// The sx library ships stb_image: `#import "vendors/stb_image/
+// stb_image.sx"` resolves through the stdlib search paths and the
+// implementation compiles through the object cache. Decodes a 2x2
+// 24-bit BMP built in memory — fully deterministic: dimensions,
+// channel count, and the top-left pixel (blue) are pinned.
+#import "modules/std.sx";
+stb :: #import "vendors/stb_image/stb_image.sx";
+
+main :: () -> i32 {
+    // BITMAPFILEHEADER (14) + BITMAPINFOHEADER (40) + 2 rows of
+    // 2 BGR pixels padded to 4-byte rows (8 each) = 70 bytes.
+    // Bottom row: red, green; top row: blue, white (BMP is bottom-up).
+    bmp : [70]u8 = .{
+        66, 77, 70, 0, 0, 0, 0, 0, 0, 0, 54, 0, 0, 0,
+        40, 0, 0, 0, 2, 0, 0, 0, 2, 0, 0, 0, 1, 0, 24, 0,
+        0, 0, 0, 0, 16, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 255, 0, 255, 0, 0, 0,
+        255, 0, 0, 255, 255, 255, 0, 0,
+    };
+
+    w : i32 = 0;
+    h : i32 = 0;
+    ch : i32 = 0;
+    img := stb.stbi_load_from_memory(@bmp[0], 70, @w, @h, @ch, 3);
+    if xx img == 0 {
+        print("decode failed\n");
+        return 1;
+    }
+    p : [*]u8 = xx img;
+    print("decoded {}x{} ({} channels)\n", w, h, ch);
+    print("top-left pixel: {} {} {}\n", p[0], p[1], p[2]);
+    stb.stbi_image_free(xx img);
+    0
+}

examples/vendor/1626-vendor-stb-truetype-metrics.sx

@@ -0,0 +1,36 @@
+// The sx library ships stb_truetype: `#import "vendors/stb_truetype/
+// stb_truetype.sx"` resolves through the stdlib search paths and the
+// implementation compiles through the object cache. Loads the system
+// Helvetica collection and pins INVARIANTS only (font versions vary
+// across macOS releases): init succeeds, the pixel-height scale is
+// positive, the ascender is positive and the descender negative.
+#import "modules/std.sx";
+fs :: #import "modules/std/fs.sx";
+tt :: #import "vendors/stb_truetype/stb_truetype.sx";
+
+main :: () -> i32 {
+    data := fs.read_file("/System/Library/Fonts/Helvetica.ttc");
+    if data == null {
+        print("font missing\n");
+        return 1;
+    }
+    bytes := data!;
+
+    off := tt.stbtt_GetFontOffsetForIndex(bytes.ptr, 0);
+    print("font offset >= 0: {}\n", off >= 0);
+
+    info : *void = xx context.allocator.alloc_bytes(256);
+    ok := tt.stbtt_InitFont(info, bytes.ptr, off);
+    print("init ok: {}\n", ok != 0);
+
+    px : f32 = 32.0;
+    scale := tt.stbtt_ScaleForPixelHeight(info, px);
+    print("scale > 0: {}\n", scale > 0.0);
+
+    ascent : i32 = 0;
+    descent : i32 = 0;
+    linegap : i32 = 0;
+    tt.stbtt_GetFontVMetrics(info, @ascent, @descent, @linegap);
+    print("ascent > 0, descent < 0: {} {}\n", ascent > 0, descent < 0);
+    0
+}

examples/vendor/1627-vendor-kbts-shape-context.sx

@@ -0,0 +1,28 @@
+// The sx library ships kb_text_shape: `#import "vendors/kb_text_shape/
+// kb_text_shape.sx"` resolves through the stdlib search paths and the
+// ~30k-line implementation compiles through the object cache (decls
+// come from the curated c/kbts_api.h). Pins INVARIANTS only: a shape
+// context constructs, the system Helvetica loads as a shaping font,
+// and teardown is clean.
+#import "modules/std.sx";
+fs :: #import "modules/std/fs.sx";
+kb :: #import "vendors/kb_text_shape/kb_text_shape.sx";
+
+main :: () -> i32 {
+    data := fs.read_file("/System/Library/Fonts/Helvetica.ttc");
+    if data == null {
+        print("font missing\n");
+        return 1;
+    }
+    bytes := data!;
+
+    ctx := kb.kbts_CreateShapeContext(xx 0, xx 0);
+    print("context created: {}\n", xx ctx != 0);
+
+    font := kb.kbts_ShapePushFontFromMemory(ctx, xx bytes.ptr, xx bytes.len, 0);
+    print("font pushed: {}\n", xx font != 0);
+
+    kb.kbts_DestroyShapeContext(ctx);
+    print("context destroyed\n");
+    0
+}

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