add examples, end-to-end tests, and Cargo.lock

Three examples:
- basic.rs: query() one-shot prompt + cost reporting.
- with_options.rs: system_prompt, model selection, effort, permission mode.
- interactive.rs: Client multi-turn session with two back-to-back sends.

Integration tests in tests/transport_end_to_end.rs spawn a tiny POSIX
shell script (tests/fake_cli/fake-claude.sh) as a stand-in for the real
claude CLI. The fake answers -v with a version, reads one user-message
frame on stdin, and emits a fixed assistant + result pair on stdout, then
blocks on stdin until close. This proves the spawn / write / read /
disconnect lifecycle works without an authenticated claude install.

Coverage:
- query() round-trip: stream yields Assistant then Result.
- Client round-trip: connect + send + drain to Result + disconnect.
- CLI-not-found surfaces as a typed Error::CliNotFound.

Cargo.lock is committed since this is, in practice, both a library and a
binary (the examples link the crate). Locking dev-deps avoids surprise
churn in CI.

tests/fake_cli/fake-claude.sh

@@ -0,0 +1,20 @@
+#!/bin/sh
+# Tiny fake `claude` CLI for integration tests. Mimics the wire protocol:
+# reads newline-delimited JSON frames on stdin, emits assistant + result
+# frames on stdout. Echoes whatever the user said.
+#
+# Args: ignores everything except `-v` (prints a version, exits 0).
+
+if [ "$1" = "-v" ]; then
+    echo "2.1.0 (Claude Code)"
+    exit 0
+fi
+
+# Read one user-message frame (we don't actually parse it — just block on stdin).
+# After the first newline we emit one assistant message + one result message.
+read -r FIRST_LINE
+printf '{"type":"assistant","message":{"role":"assistant","content":[{"type":"text","text":"hello from fake"}],"model":"fake-model"},"session_id":"s1","uuid":"u1"}\n'
+printf '{"type":"result","subtype":"success","duration_ms":1,"duration_api_ms":1,"is_error":false,"num_turns":1,"session_id":"s1","total_cost_usd":0.0001}\n'
+
+# Stay alive until stdin closes (so the parent can drain stdout cleanly).
+cat > /dev/null