feat(sdk,plugins): ajoute capability tooling et services runtime publics (workspace/terminal/tasks)

- capability manifeste tooling supportée backend + transport runtime catalog
- ctx.services publique côté SDK/runtime, gated par tooling
- surface honnête: workspace, terminal, et tasks en observation/contrôle uniquement
- docs/exemple/tests mis à jour
- QA PASS sur feature/sdk-plugin-tooling-build-debug-surface

sdk/IdeaSDK/README.md

@@ -6,6 +6,7 @@ This first version intentionally stays small:
 
 - public manifest types for `idea-plugin.json`;
 - public runtime types for plugin modules exposing `activate(ctx)`;
+- a stable `ctx.services` facade for workspace, background task and terminal operations;
 - a lightweight manifest validator;
 - a minimal `examples/hello-plugin` plugin.
 
@@ -69,6 +70,42 @@ export function activate(ctx: ActivateContext): void {
 }
 ```
 
+## Runtime Services
+
+Plugins declaring the `tooling` capability receive `ctx.services`. Plugins
+without that capability do not receive this facade. Prefer `ctx.services` over
+IdeA's internal runtime objects when it is available:
+
+```ts
+import type { ActivateContext } from "@idea/plugin-sdk";
+
+export async function activate(ctx: ActivateContext): Promise<void> {
+  const project = await ctx.services?.workspace.getCurrentProject();
+  ctx.logger.info("current project", project);
+
+  const task = await ctx.services?.tasks.getStatus("task-id");
+  ctx.logger.info("task status", task?.status);
+
+  const terminal = await ctx.services?.terminal.open({ rows: 24, cols: 80 });
+  await terminal?.write(new TextEncoder().encode("echo hello\\r"));
+}
+```
+
+Current terminal scope is intentionally minimal: it opens or reattaches a shell
+PTY, writes bytes, resizes, detaches and closes. The background task service is
+observation/control only in this SDK version: `list`, `getStatus`, `attachOutput`,
+`cancel` and `retry` operate on existing tasks visible through IdeA's Work read
+model. Starting new background tasks is not part of the public plugin API in this
+lot.
+
+Declare the additive `tooling` capability to receive `ctx.services` at runtime:
+
+```json
+{
+  "capabilities": ["ui", "tooling"]
+}
+```
+
 ## Manifest Validation
 
 ```ts