chore: version 1.51.0, path-dep the wasm examples, README notes

- socktop, socktop_agent, socktop_connector -> 1.51.0.
- socktop_wasm_test and zellij_socktop_plugin consume the in-repo
  connector via path deps so wasm-feature API drift is caught at PR time
  instead of after publish. Immediately proved out: the wasm requests
  module needed the new sampled_at_ms field, invisible to native builds.
- zellij plugin gains the standalone [workspace] marker (it could not be
  cargo-checked in-tree at all before). NOTE: its lib.rs has pre-existing
  compile errors unrelated to the connector (static mut STATE conflicts
  with register_plugin!, missing BTreeMap import) — needs its own rework,
  out of scope here.
- README: sampled_at_ms in the example payload.

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

zellij_socktop_plugin/Cargo.toml

@@ -3,6 +3,9 @@ name = "zellij_socktop_plugin"
 version = "0.1.0"
 edition = "2021"
 
+# Standalone package, not part of the parent workspace (same as socktop_wasm_test)
+[workspace]
+
 [lib]
 crate-type = ["cdylib"]
 
@@ -10,7 +13,7 @@ crate-type = ["cdylib"]
 zellij-tile = "0.40.0"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
-socktop_connector = { version = "0.1.5", default-features = false, features = ["wasm"] }
+socktop_connector = { path = "../socktop_connector", default-features = false, features = ["wasm"] }
 futures = "0.3"
 
 [dependencies.chrono]