test(multifile): cover imports, shared globals and exception propagation

Allow fixtures to pass ordered source lists and require file-qualified
negative diagnostics. Add native and runner cases for cross-unit calls,
global mutation and shadowing, transitive imports, types, MAIN status,
exception catches, runtime failures and destructor unwinding.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

3 files changed, 20 insertions, 0 deletions

diff --git a/tests/iii/multifile-duplicate-function/case.json b/tests/iii/multifile-duplicate-function/case.json
new file mode 100644
index 0000000..0d0affd
--- /dev/null
+++ b/tests/iii/multifile-duplicate-function/case.json
@@ -0,0 +1,13 @@
+{
+  "sources": [
+    "program.cps",
+    "lib.cps"
+  ],
+  "errors": [
+    {
+      "reason": "Duplicate definition value",
+      "line": 1,
+      "file": "lib.cps"
+    }
+  ]
+}
diff --git a/tests/iii/multifile-duplicate-function/lib.cps b/tests/iii/multifile-duplicate-function/lib.cps
new file mode 100644
index 0000000..7fcd8f2
--- /dev/null
+++ b/tests/iii/multifile-duplicate-function/lib.cps
@@ -0,0 +1,3 @@
+FUNCTION value RETURNS INTEGER
+RETURN 2
+ENDFUNCTION
diff --git a/tests/iii/multifile-duplicate-function/program.cps b/tests/iii/multifile-duplicate-function/program.cps
new file mode 100644
index 0000000..8488a19
--- /dev/null
+++ b/tests/iii/multifile-duplicate-function/program.cps
@@ -0,0 +1,4 @@
+OUTPUT 1
+FUNCTION Value RETURNS INTEGER
+RETURN 1
+ENDFUNCTION