Added an e2e test harness with a fake R701 device

tests/mock/mod.rs emulates the device's TCP protocol (ping, get_name,
get_total_record_count, get_record_bytes), grounded in the reverse
engineering notes at
https://nicolabelluti.me/posts/2024/05/studying-a-communication-protocol/,
so tests/e2e.rs can exercise the real R701 client against it instead of
needing a physical reader. Starts with one test (connect + ping);
more scenarios (get_name, record streaming, error cases) to follow.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Cargo.lock

@@ -251,9 +251,21 @@ dependencies = [
  "mio",
  "pin-project-lite",
  "socket2",
+ "tokio-macros",
  "windows-sys",
 ]
 
+[[package]]
+name = "tokio-macros"
+version = "2.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6328af13490e73a9b4694030fafd93f8c8c6a9dede33e821c3fc63eddf8042ba"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "tokio-stream"
 version = "0.1.19"