feat(C2): unit-first JIT symbol resolution — program-owned dylibs beat process images

runJITFromObject now takes priority dylibs (the #import c unit's
linked objects first, then #library deps in declaration order) and
attaches a per-path search generator for each AHEAD of the
process-wide fallback, so a vendored symbol can never lose to a
same-named export of an image the host process happens to carry
(libz via LLVM, libsqlite3 via CoreServices). loadLibrary reports
the name dlopen succeeded on; the c-import handle records its dylib
path; temp link inputs are per-pid so concurrent runs can't clobber
each other. Flips the C0.3 shadowing pin to from_unit: true.

src/target.zig

@@ -198,7 +198,12 @@ pub const TargetConfig = struct {
 
 /// Execute a precompiled object file in-process using LLVM's ORC JIT.
 /// Takes ownership of obj_buf. Returns the exit code from main().
-pub fn runJITFromObject(obj_buf: c.LLVMMemoryBufferRef) !u8 {
+/// `priority_dylibs` are consulted for symbols BEFORE the process-wide
+/// search, in order: dylibs that belong to the program (the `#import c`
+/// unit's linked objects, then `#library` deps in declaration order)
+/// must win over a same-named export of an image the host process
+/// happens to carry (libz via LLVM, libsqlite3 via CoreServices, ...).
+pub fn runJITFromObject(obj_buf: c.LLVMMemoryBufferRef, priority_dylibs: []const [:0]const u8) !u8 {
     // Create LLJIT with default builder (no custom TM needed — .o is precompiled)
     var jit: c.LLVMOrcLLJITRef = null;
     var err = c.LLVMOrcCreateLLJIT(&jit, null);
@@ -210,9 +215,25 @@ pub fn runJITFromObject(obj_buf: c.LLVMMemoryBufferRef) !u8 {
     }
     defer _ = c.LLVMOrcDisposeLLJIT(jit);
 
-    // Add process symbols so JIT can find libc (printf, etc.)
     const jd = c.LLVMOrcLLJITGetMainJITDylib(jit);
     const prefix = c.LLVMOrcLLJITGetGlobalPrefix(jit);
+
+    // Program-owned dylibs first (generators run in attachment order).
+    // A failed generator is skipped: resolution then degrades to the
+    // process-wide search below, exactly the pre-priority behavior.
+    for (priority_dylibs) |path| {
+        var pgen: c.LLVMOrcDefinitionGeneratorRef = null;
+        err = c.LLVMOrcCreateDynamicLibrarySearchGeneratorForPath(&pgen, path.ptr, prefix, null, null);
+        if (err != null) {
+            const msg = c.LLVMGetErrorMessage(err);
+            defer c.LLVMDisposeErrorMessage(msg);
+            std.debug.print("warning: JIT could not search '{s}': {s}\n", .{ path, std.mem.span(msg) });
+            continue;
+        }
+        c.LLVMOrcJITDylibAddGenerator(jd, pgen);
+    }
+
+    // Process-wide fallback so the JIT finds libc (printf, etc.)
     var gen: c.LLVMOrcDefinitionGeneratorRef = null;
     err = c.LLVMOrcCreateDynamicLibrarySearchGeneratorForProcess(&gen, prefix, null, null);
     if (err != null) {