fix: require a successful probe result before handoff

Adapt the bounded probe-completion foundation from PR #130 by aksalatdev (source commit 535202bebe038fa1e0648f5df809d5ccfc26d071), not its mixed stream-salvage implementation.

Require a non-failed call followed by a matching probe_done result with neither isError nor explicit details.ok:false. Preserve older clean acknowledgments, saved attempts, and all existing handoff/retry/provider policies. Share the native completion seam with phase detection and exclude explicit refusals from UI phases.

Verify retained failed-probe Retry recovery with real agent/tool composition and synthetic engines: one fresh conclusion, one handoff, then teacher selection, without stored-tool replay. Focused tests 58/58; full tests 2473/2473; typecheck and full ESLint pass in isolated storage with scrubbed provider credentials.

Co-authored-by: aksalatdev <73862605+aksalatdev@users.noreply.github.com>

src/agent/tools/probe.ts

@@ -42,8 +42,9 @@ function probeConcluded(messages: readonly LhMessage[]): boolean {
  *     live), so the agent sees the fixed PROBE_DONE_ACK_TEXT — never an
  *     echo. details = {ok:true} only.
  *
- * The first probe_done in the transcript is also the construction seam:
- * from that message on, every request builds the TEACHER agent.
+ * The first concluded probe_done (non-failed call plus matching successful
+ * result) is also the construction seam: from that result on, every request
+ * builds the TEACHER agent. Bare calls and refused results keep probing.
  */
 export function probeDoneTool(ctx: ProbeDoneContext): Record<string, AgentTool<any>> {
 	return {