feat: provide v2 Plugin Component contracts and offline validation

Validate exact Component interfaces and static Tool/DCDL schemas without guest execution. Share canonical archive packing and independent package/artifact verification; build real pure and HTTPS PDK fixtures and retire v1/Service authoring stubs.

crates/plugin-pdk/tests/fixtures/component-tool-source.txt

@@ -1,38 +0,0 @@
-//! Minimal Component Model Tool plugin authoring sketch using `yoi-plugin-pdk`.
-//!
-//! Build this as a `wasm32-unknown-unknown` cdylib with Component Model tooling
-//! and package the adapted component as `plugin.component.wasm`.
-
-use serde::{Deserialize, Serialize};
-use yoi_plugin_pdk::wit_bindgen;
-use yoi_plugin_pdk::{ToolContext, ToolError, ToolOutput};
-
-wit_bindgen::generate!({
-    world: "tool",
-    path: "../../../resources/plugin/wit",
-    generate_all,
-    runtime_path: "yoi_plugin_pdk::wit_bindgen::rt",
-});
-
-#[derive(Debug, Deserialize)]
-struct EchoInput {
-    text: String,
-}
-
-#[derive(Debug, Serialize)]
-struct EchoOutput<'a> {
-    tool: &'a str,
-    text: String,
-}
-
-fn handle_echo(ctx: ToolContext, input: EchoInput) -> Result<ToolOutput, ToolError> {
-    ToolOutput::json(
-        format!("{} ok", ctx.tool_name()),
-        EchoOutput {
-            tool: ctx.tool_name(),
-            text: input.text,
-        },
-    )
-}
-
-yoi_plugin_pdk::export_component_tool!(Plugin, handle_echo);