fix: report errors to progress comment when agent fails without throwing (#376)

* fix: report errors to progress comment when agent fails without throwing

when an agent returns success: false without throwing (e.g., opencode exits
with code 0 despite provider errors), the catch block in main.ts is never
reached, leaving the progress comment stuck on "leaping into action."

two fixes:
- opencode: return success: false when 0 events processed and a provider
  error was detected (converts silent failures to explicit failures)
- main.ts: after handleAgentResult, check if the progress comment was ever
  updated — if not, report the error to the comment as a safety net

Co-authored-by: Cursor <cursoragent@cursor.com>

* address review: use result directly and force failure on unreported progress

* refactor: move safety-net logic into handleAgentResult

---------

Co-authored-by: pullfrog[bot] <226033991+pullfrog[bot]@users.noreply.github.com>
Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: Anna Bocharova <robin_tail@me.com>

utils/run.ts

@@ -1,13 +1,37 @@
 import type { AgentResult } from "../agents/shared.ts";
 import type { MainResult } from "../main.ts";
+import type { ToolState } from "../mcp/server.ts";
 import { log } from "./cli.ts";
+import { reportErrorToComment } from "./errorReport.ts";
 
-export function handleAgentResult(result: AgentResult): MainResult {
-  if (!result.success) {
+export interface HandleAgentResultParams {
+  result: AgentResult;
+  toolState: ToolState;
+  silent: boolean | undefined;
+}
+
+export async function handleAgentResult(ctx: HandleAgentResultParams): Promise<MainResult> {
+  if (!ctx.result.success) {
     return {
       success: false,
-      error: result.error || "Agent execution failed",
-      output: result.output!,
+      error: ctx.result.error || "Agent execution failed",
+      output: ctx.result.output!,
+    };
+  }
+
+  if (!ctx.toolState.wasUpdated && ctx.toolState.progressCommentId && !ctx.silent) {
+    const error = ctx.result.error || "agent completed without reporting progress";
+    try {
+      await reportErrorToComment({
+        toolState: ctx.toolState,
+        error,
+        title: "Error",
+      });
+    } catch {}
+    return {
+      success: false,
+      error,
+      output: ctx.result.output || "",
     };
   }
 
@@ -15,6 +39,6 @@ export function handleAgentResult(result: AgentResult): MainResult {
 
   return {
     success: true,
-    output: result.output || "",
+    output: ctx.result.output || "",
   };
 }