init: Scaffold expected crates with initial dependencies.

crates/pikl-test-macros/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "pikl-test-macros"
+description = "Test DSL proc macro for pikl-menu. Dev-only, never shipped."
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[lib]
+proc-macro = true
+
+# Proc macros have different conventions (panics are compile errors, etc.)
+# so we don't inherit workspace lints here.
+
+[dependencies]
+syn = { version = "2", features = ["full", "extra-traits"] }
+quote = "1"
+proc-macro2 = "1"