feat: add workspace skeleton and server configuration validation

Cargo.toml

@@ -0,0 +1,12 @@
+[workspace]
+# Format crates (gemtext, wap, text) join at the milestone that implements them.
+members = ["core", "bin"]
+default-members = ["bin"]
+resolver = "2"
+
+# No `panic = "abort"`: a thread-per-connection server must survive one
+# malformed document, and the handler boundary catches unwinds to log the cause.
+[profile.release]
+lto = true
+codegen-units = 1
+strip = true