refactor: deduplicate tool code and remove dead stubs (#98)

* refactor: deduplicate tool parameter extraction and remove dead stub tools

Delete 4 never-registered stub tools (marketplace, restaurant, ecommerce,
taskrabbit) removing ~625 lines of dead code. Add require_str/require_param
helpers to tool.rs and refactor ~30 call sites across 10 tool files from
4-6 line inline extractions to single-line calls. Consolidate worker HTTP
client with get_json/post_json helpers, reducing boilerplate in 4 methods.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix: return JSON from orchestrator /complete endpoint

The report_complete handler returned bare StatusCode::OK (no body),
which broke the post_json helper that expects a JSON response.
Return {"status": "ok"} for consistency with other worker endpoints.

Addresses review feedback on PR #98.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 <[email protected]>

src/orchestrator/api.rs

@@ -202,7 +202,7 @@ async fn report_complete(
     State(state): State<OrchestratorState>,
     Path(job_id): Path<Uuid>,
     Json(report): Json<CompletionReport>,
-) -> Result<StatusCode, StatusCode> {
+) -> Result<Json<serde_json::Value>, StatusCode> {
     if report.success {
         tracing::info!(
             job_id = %job_id,
@@ -223,7 +223,7 @@ async fn report_complete(
     };
     let _ = state.job_manager.complete_job(job_id, result).await;
 
-    Ok(StatusCode::OK)
+    Ok(Json(serde_json::json!({"status": "ok"})))
 }
 
 // -- Sandbox job event handlers --