feat(component): add KV capability probe

Add a small Component that imports wasmeld:kv/store@0.1.0 and exercises get, set, and delete through a byte-oriented test protocol.

Pin service and KV WIT dependencies in wit.lock while keeping generated wit/deps content out of source control.

components/kv-probe/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "kv-probe-component"
+version = "0.1.0"
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+
+[package.metadata.wasmeld]
+id = "kv-probe"
+world = "component:kv-probe/kv-probe-component@0.1.0"
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+wit-bindgen.workspace = true

components/kv-probe/src/lib.rs

@@ -0,0 +1,63 @@
+mod bindings {
+    wit_bindgen::generate!({
+        path: "wit",
+        world: "kv-probe-component",
+        generate_all,
+    });
+}
+
+use bindings::wasmeld::kv::store;
+
+struct KvProbe;
+
+impl bindings::Guest for KvProbe {
+    fn init(_config: Vec<u8>) -> Result<(), bindings::ServiceError> {
+        Ok(())
+    }
+
+    fn invoke(input: Vec<u8>) -> Result<Vec<u8>, bindings::ServiceError> {
+        if let Some(key) = input.strip_prefix(b"get:") {
+            let key = parse_key(key)?;
+            return store::get(&key)
+                .map(|value| value.unwrap_or_default())
+                .map_err(kv_error);
+        }
+
+        if let Some(command) = input.strip_prefix(b"set:") {
+            let separator = command
+                .iter()
+                .position(|byte| *byte == b':')
+                .ok_or_else(|| {
+                    bindings::ServiceError::CallFailed(
+                        "set command must be set:<key>:<value>".to_owned(),
+                    )
+                })?;
+            let key = parse_key(&command[..separator])?;
+            let value = command[separator + 1..].to_vec();
+            store::set(&key, &value).map_err(kv_error)?;
+            return Ok(Vec::new());
+        }
+
+        if let Some(key) = input.strip_prefix(b"delete:") {
+            let key = parse_key(key)?;
+            store::delete(&key).map_err(kv_error)?;
+            return Ok(Vec::new());
+        }
+
+        Err(bindings::ServiceError::CallFailed(
+            "expected get:<key>, set:<key>:<value>, or delete:<key>".to_owned(),
+        ))
+    }
+}
+
+fn parse_key(bytes: &[u8]) -> Result<String, bindings::ServiceError> {
+    core::str::from_utf8(bytes)
+        .map(str::to_owned)
+        .map_err(|_| bindings::ServiceError::CallFailed("key must be valid UTF-8".to_owned()))
+}
+
+fn kv_error(error: store::KvError) -> bindings::ServiceError {
+    bindings::ServiceError::CallFailed(format!("KV operation failed: {error:?}"))
+}
+
+bindings::export!(KvProbe with_types_in bindings);

components/kv-probe/wasmeld.toml

@@ -0,0 +1,11 @@
+schema_version = 1
+
+[dependencies]
+"wasmeld:kv" = "0.1.0"
+"wasmeld:service" = "0.1.0"
+
+[replace."wasmeld:kv"]
+path = "../../wit/kv"
+
+[replace."wasmeld:service"]
+path = "../../wit/service"

components/kv-probe/wit.lock

@@ -0,0 +1,15 @@
+schema_version = 1
+
+[[package]]
+name = "wasmeld:kv"
+version = "0.1.0"
+source = "path+../../wit/kv"
+sha256 = "6dc3a84dc03c7104aa8b305518466c95e4440e1031c4bef3b59843f40f24d0fb"
+replaced = true
+
+[[package]]
+name = "wasmeld:service"
+version = "0.1.0"
+source = "path+../../wit/service"
+sha256 = "d5497307bbcd1e159f7707f385b488a6f2e26362d5256d5bc1080ac603a51305"
+replaced = true

components/kv-probe/wit/world.wit

@@ -0,0 +1,6 @@
+package component:kv-probe@0.1.0;
+
+world kv-probe-component {
+  include wasmeld:service/service-component@0.1.0;
+  import wasmeld:kv/store@0.1.0;
+}