chore: Add agentic coding tooling

.crosslink/rules/zig.md

@@ -0,0 +1,48 @@
+### Zig Best Practices
+
+#### Code Style
+- Follow Zig Style Guide
+- Use `const` by default; `var` only when mutation needed
+- Prefer slices over pointers when possible
+- Use meaningful names; avoid single-letter variables
+
+```zig
+// GOOD: Clear, idiomatic Zig
+const User = struct {
+    id: []const u8,
+    name: []const u8,
+};
+
+fn findUser(allocator: std.mem.Allocator, id: []const u8) !?User {
+    const user = try repository.find(allocator, id);
+    return user;
+}
+```
+
+#### Error Handling
+- Use error unions (`!T`) for fallible operations
+- Handle errors with `try`, `catch`, or explicit checks
+- Create meaningful error sets
+
+```zig
+// GOOD: Proper error handling
+const ConfigError = error{
+    FileNotFound,
+    ParseError,
+    OutOfMemory,
+};
+
+fn loadConfig(allocator: std.mem.Allocator) ConfigError!Config {
+    const file = std.fs.cwd().openFile("config.json", .{}) catch |err| {
+        return ConfigError.FileNotFound;
+    };
+    defer file.close();
+    // ...
+}
+```
+
+#### Memory Safety
+- Always pair allocations with deallocations
+- Use `defer` for cleanup
+- Prefer stack allocation when size is known
+- Use allocators explicitly; never use global state