Optimize the code

[kerthcet]

What this PR does / why we need it

Which issue(s) this PR fixes

Fixes #

Special notes for your reviewer

Does this PR introduce a user-facing change?

[Copilot]

Pull request overview

Despite the title "Optimize the code", this PR is primarily a feature/refactor change that introduces WebSocket subprotocol versioning (sandd.v1) between the daemon client and the server, renames the public Python execute_command keyword from timeout_secs to timeout, and reduces noise in the heartbeat monitor log. It also tidies up trailing whitespace in docs/PROTOCOL.md and expands the simple command example to iterate over all daemons and test multiple commands.

Changes:

• Add WebSocket Sec-WebSocket-Protocol: sandd.v1 negotiation on both server (Axum handler) and daemon (tokio-tungstenite client request), with docs in PROTOCOL.md.
• Rename the public Python execute_command parameter timeout_secs → timeout in PyO3 binding, Python wrapper, README, and the example script (wire protocol field timeout_secs is unchanged).
• Simplify the heartbeat monitor log to only show registry.count(), and reorder route registration.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
server/src/server.rs	Adds HeaderMap + subprotocol negotiation in websocket_handler; simplifies heartbeat log; reorders /stats and /health routes.
server/src/lib.rs	Renames PyO3 keyword timeout_secs → timeout; still serializes to wire field timeout_secs.
sandd/src/main.rs	Builds a manual IntoClientRequest to send Sec-WebSocket-Protocol: sandd.v1, and logs the negotiated protocol from the response.
python/sandd/init.py	Updates execute_command signature and docstring to use timeout.
README.md	Updates example to use timeout= kwarg.
examples/simple_command_test.py	Iterates over all daemons and runs multiple test commands (success, intentional error, echo).
docs/PROTOCOL.md	Documents subprotocol versioning; strips trailing whitespace on Direction lines.

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