Node SDK: wire up snapshot

[justinmclean]

The Rust client has SystemClient::snapshot (core/common/src/traits/system_client.rs), which returns a compressed snapshot of server state for debugging. It is the only client call the Node SDK does not have. The command code is already in foreign/node/src/wire/command.code.ts (GetSnapshot: 11, marked @TODO), but nothing uses it.

What to do

• Add foreign/node/src/wire/system/snapshot.command.ts, following get-stats.command.ts in the same folder. The request and response formats are in core/binary_protocol/src/requests/system/get_snapshot.rs and core/binary_protocol/src/responses/system/get_snapshot.rs.
• Export it from system/index.ts and register it in foreign/node/src/wire/command-set.ts next to getStats.
• Remove the @TODO on the GetSnapshot entry.
• Add a unit test for the serialisation, and an e2e test in foreign/node/src/e2e/tcp.raw.e2e.ts next to the getStats one.

Done when

snapshot returns a non-empty result against a running server, and the new tests pass.

[rk-roshan-kr]

Hi @justinmclean @hubcio, I would like to work on this issue. Could you please assign it to me?

Plan:

• Add foreign/node/src/wire/system/snapshot.command.ts implementing the binary wire protocol ([compression:1][types_count:1][snapshot_type:1]*) and handling the raw ZIP archive response.
• Export it from system/index.ts and register it in command-set.ts under systemAPI next to getStats.
• Remove the @TODO on command code 11 in command.code.ts.
• Add serialization/deserialization unit tests in snapshot.command.test.ts and integration checks in tcp.raw.e2e.ts.

I have the implementation, unit tests, and TypeScript builds verified locally.

[hubcio]

@rk-roshan-kr assigned