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/cimport/1618-cimport-named-defines.sx

@@ -0,0 +1,18 @@
+// Pins the NAMED `#import c` block (PLAN-C C0.1): the block's name
+// namespaces the decls synthesized from `#include`, and `#define` /
+// `#flags` entries reach the unit's clang invocation — the macro decides
+// what cdef_value answers.
+#import "modules/std.sx";
+
+cu :: #import c {
+    #include "1618-cimport-named-defines/cdef.h";
+    #source  "1618-cimport-named-defines/cdef.c";
+    #define  "CDEF_BASE=42";
+    #flags   "-O2";
+};
+
+main :: () -> i32 {
+    print("value = {}\n", cu.cdef_value());
+    print("doubled = {}\n", cu.cdef_doubled(21));
+    0
+}

examples/cimport/1618-cimport-named-defines/cdef.c

@@ -0,0 +1,6 @@
+#include "cdef.h"
+#ifndef CDEF_BASE
+#define CDEF_BASE 1
+#endif
+int cdef_value(void) { return CDEF_BASE; }
+int cdef_doubled(int x) { return x * 2; }

examples/cimport/1618-cimport-named-defines/cdef.h

@@ -0,0 +1,5 @@
+#ifndef CDEF_H
+#define CDEF_H
+int cdef_value(void);
+int cdef_doubled(int x);
+#endif

examples/cimport/1619-cimport-source-only.sx

@@ -0,0 +1,17 @@
+// Pins the curated-bindings shape (PLAN-C C0.2): a `#source`-only unit
+// (no `#include`, so no auto-synthesized decls) paired with a
+// hand-written `extern` decl naming the unit. Works in JIT and AOT
+// today — but see 1620: the unit ref is not yet validated or scoped,
+// so the symbol actually resolves globally, not through the unit.
+#import "modules/std.sx";
+
+only :: #import c {
+    #source "1619-cimport-source-only/only.c";
+};
+
+only_answer :: () -> i32 extern only "only_answer";
+
+main :: () -> i32 {
+    print("answer = {}\n", only_answer() + 1);
+    0
+}

examples/cimport/1619-cimport-source-only/only.c

@@ -0,0 +1 @@
+int only_answer(void) { return 41; }

examples/cimport/1621-cimport-shadow-os-lib.sx

@@ -0,0 +1,18 @@
+// Unit-first JIT resolution (PLAN-C C2): a `#source` unit defining a
+// symbol that ALSO lives in an OS image already loaded into the
+// compiler process (libz, via libLLVM) still wins — the unit's dylib
+// is a priority symbol-search target ahead of the process-wide
+// fallback. The unit's zlibCompileFlags answers 0xDEADBEEF; the OS
+// one answers real flag bits, so `true` proves the unit won.
+// Regression (PLAN-C C0.3 xfail, flipped by C2.1).
+#import "modules/std.sx";
+
+zshadow :: #import c {
+    #include "1621-cimport-shadow-os-lib/shadow.h";
+    #source  "1621-cimport-shadow-os-lib/shadow.c";
+};
+
+main :: () -> i32 {
+    print("from_unit: {}\n", zshadow.zlibCompileFlags() == 3735928559);
+    0
+}

examples/cimport/1621-cimport-shadow-os-lib/shadow.c

@@ -0,0 +1 @@
+unsigned long zlibCompileFlags(void) { return 3735928559UL; }

examples/cimport/1621-cimport-shadow-os-lib/shadow.h

@@ -0,0 +1 @@
+unsigned long zlibCompileFlags(void);

examples/cimport/1622-cimport-unit-bound-defines.sx

@@ -0,0 +1,17 @@
+// `#define`/`#flags` reach a unit whose ONLY consumer is hand-curated
+// `extern` decls (PLAN-C C3.3) — no `#include`, no auto-synthesis:
+// the macro decides what the unit-bound decl answers.
+#import "modules/std.sx";
+
+unit :: #import c {
+    #define "UNIT_BASE=33";
+    #flags  "-O2";
+    #source "1622-cimport-unit-bound-defines/unit.c";
+};
+
+unit_answer :: () -> i32 extern unit "unit_answer";
+
+main :: () -> i32 {
+    print("unit answer = {}\n", unit_answer());
+    0
+}

examples/cimport/1622-cimport-unit-bound-defines/unit.c

@@ -0,0 +1,4 @@
+#ifndef UNIT_BASE
+#define UNIT_BASE 1
+#endif
+int unit_answer(void) { return UNIT_BASE; }

examples/cimport/1623-cimport-unit-in-aliased-module.sx

@@ -0,0 +1,11 @@
+// A named `#import c` unit declared INSIDE an aliased module (so the
+// unit's namespace nests two deep in the merged tree) still compiles
+// and links — collectCImportSources recurses through namespaces, the
+// same way #library collection does (issue 0130's pattern).
+#import "modules/std.sx";
+m :: #import "1623-cimport-unit-in-aliased-module/mod.sx";
+
+main :: () -> i32 {
+    print("nested unit answer = {}\n", m.answer_via_mod());
+    0
+}

examples/cimport/1623-cimport-unit-in-aliased-module/inmod.c

@@ -0,0 +1 @@
+int unit_in_mod_answer(void) { return 54; }

examples/cimport/1623-cimport-unit-in-aliased-module/mod.sx

@@ -0,0 +1,10 @@
+// A module that owns a named C unit + a hand-curated binding.
+#import "modules/std.sx";
+
+cunit :: #import c {
+    #source "inmod.c";
+};
+
+unit_in_mod_answer :: () -> i32 extern cunit "unit_in_mod_answer";
+
+answer_via_mod :: () -> i32 { return unit_in_mod_answer(); }

examples/cimport/1628-cimport-duplicate-export.sx

@@ -0,0 +1,20 @@
+// Two `#import c` units defining the same exported symbol is a
+// compile-time diagnostic naming both sources — previously it died
+// inside the JIT dylib link (or the AOT link) with raw linker spew.
+// All units share one link namespace; per-unit symbol isolation is
+// PLAN-C C3.2 (deferred).
+#import "modules/std.sx";
+
+ua :: #import c {
+    #source "1628-cimport-duplicate-export/a.c";
+};
+ub :: #import c {
+    #source "1628-cimport-duplicate-export/b.c";
+};
+
+clash :: () -> i32 extern ua "clash";
+
+main :: () -> i32 {
+    print("{}\n", clash());
+    0
+}

examples/cimport/1628-cimport-duplicate-export/a.c

@@ -0,0 +1 @@
+int clash(void) { return 1; }

examples/cimport/1628-cimport-duplicate-export/b.c

@@ -0,0 +1 @@
+int clash(void) { return 2; }

examples/cimport/expected/1618-cimport-named-defines.exit

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

examples/cimport/expected/1618-cimport-named-defines.stderr

@@ -0,0 +1 @@
+

examples/cimport/expected/1618-cimport-named-defines.stdout

@@ -0,0 +1,2 @@
+value = 42
+doubled = 42

examples/cimport/expected/1619-cimport-source-only.exit

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

examples/cimport/expected/1619-cimport-source-only.stderr

@@ -0,0 +1 @@
+

examples/cimport/expected/1619-cimport-source-only.stdout

@@ -0,0 +1 @@
+answer = 42

examples/cimport/expected/1621-cimport-shadow-os-lib.exit

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

examples/cimport/expected/1621-cimport-shadow-os-lib.stderr

@@ -0,0 +1 @@
+

examples/cimport/expected/1621-cimport-shadow-os-lib.stdout

@@ -0,0 +1 @@
+from_unit: true

examples/cimport/expected/1622-cimport-unit-bound-defines.exit

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

examples/cimport/expected/1622-cimport-unit-bound-defines.stderr

@@ -0,0 +1 @@
+

examples/cimport/expected/1622-cimport-unit-bound-defines.stdout

@@ -0,0 +1 @@
+unit answer = 33

examples/cimport/expected/1623-cimport-unit-in-aliased-module.exit

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

examples/cimport/expected/1623-cimport-unit-in-aliased-module.stderr

@@ -0,0 +1 @@
+

examples/cimport/expected/1623-cimport-unit-in-aliased-module.stdout

@@ -0,0 +1 @@
+nested unit answer = 54

examples/cimport/expected/1628-cimport-duplicate-export.exit

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

examples/cimport/expected/1628-cimport-duplicate-export.stderr

@@ -0,0 +1 @@
+error: C symbol 'clash' is defined by multiple '#import c' sources: 'examples/cimport/1628-cimport-duplicate-export/a.c' and 'examples/cimport/1628-cimport-duplicate-export/b.c' — all units share one link namespace

examples/cimport/expected/1628-cimport-duplicate-export.stdout

@@ -0,0 +1 @@
+