[Bug] Workflow call_webhook action never delivers — silent, no error, no run record

**Describe the bug**

A workflow step with `action: call_webhook` never delivers an HTTP request to its target URL, with no error surfaced anywhere: the workflow appears to succeed, any preceding `send_message` step in the same run posts normally, but the `call_webhook` step's request is never received by the destination.

**Steps to reproduce**

1. Create a webhook-triggered workflow with a `call_webhook` step (tested both as the only step in an isolated workflow, and chained after a working `send_message` step in a multi-step workflow).
2. Point the `call_webhook` URL at a destination you can independently observe receiving requests.
3. Trigger the workflow via `buzz workflows trigger --workflow ` and, separately, via `POST /hooks/{workflow_id}`.
4. Wait 20+ seconds.
5. Observe: the destination receives zero requests.

We tested three independent destinations to rule out anything endpoint-specific, all with the same zero-delivery result:
- A local SSH tunnel (`localhost.run`) fronting a real local server.
- A public `httpbin.org` echo endpoint.
- A `webhook.site` request catcher, independently confirmed (via a separate fetch) to be receiving zero requests, not just "unreachable from our side."

We also isolated the two action types from each other with single-step throwaway workflows:
- A workflow with only a `send_message` step: posts to the channel reliably, every time.
- A workflow with only a `call_webhook` step (same trigger mechanism, same account): zero deliveries, every time.

This rules out trigger delivery, account/auth, and workflow-YAML syntax as the cause — the discrepancy is specific to the `call_webhook` action itself.

Related, possibly the same underlying issue: `buzz workflows runs --workflow ` returns `[]` even for a workflow run that is confirmed to have executed (e.g. its `send_message` step's post is visibly sitting in the channel) — so there is no CLI-visible run/step history to inspect for a `call_webhook` failure reason either. This may be the same gap referenced in #2980 / #4478 (workflow run history always empty), in which case a fix there might also surface diagnostics for this issue — but the *delivery* failure and the *history* failure are two distinct observed symptoms and this issue is specifically about the former.

**Expected behavior**

`call_webhook` should deliver the configured HTTP request to its target, or if it fails, the failure should be visible somewhere (run history, an error event in the channel, CLI output, logs) rather than silently no-op'ing.

**Version and platform**

- Buzz version: hosted deployment
- Reproduced independently by two separate agents/accounts on the same hosted relay, same day (2026-08-06)

**Logs / additional context**

No approval-gate explanation found either — `buzz workflows approve` exists as a command but no approval token or pending-approval indicator ever surfaced for these runs.

Workaround we shipped: removed the `call_webhook` step from our workflow entirely and moved that responsibility to a live Desktop-managed agent identity making its own outbound HTTP call instead of relying on the workflow action — works reliably, but defeats the purpose of having a native webhook-callback workflow action.

Start by reproducing the failure with `buzz workflows trigger --workflow ` and `POST /hooks/{workflow_id}`, then inspect the workflow execution path for `call_webhook` and the `buzz workflows runs --workflow ` entry point. Done means the configured request is delivered, or a failed delivery and its run/step status are visible through an existing diagnostic path.

Written by the indexing model from the issue text.