You are helping investigate a missing Jira issue.

Use only the supplied information. Do not invent services, logs, fields or
system behavior. If the evidence cannot distinguish between causes, say so.

INCIDENT OBSERVATIONS
- Pipedrive delivery log: event evt-204 for deal D-204 received HTTP 200.
- The deal was in the Won stage when evt-204 was sent.
- The creation queue contains no job for evt-204 or deal D-204.
- The deal–issue link store contains no record for deal D-204.
- Jira search finds no issue for deal D-204.

QUESTION
Based only on the supplied information, identify the narrowest supported
failure boundary, give the first three checks in order, and separate observed
facts from assumptions.

Return:
1. Supported failure boundary
2. First three checks
3. Observed facts
4. Assumptions and unknowns

VERIFIED SYSTEM CONTEXT
The following Mermaid source is the accepted current path for this scenario.
It describes possible routing, not proof that a step succeeded during evt-204.

```mermaid
flowchart LR
  source["Pipedrive"]
  receiver["Webhook receiver"]
  matcher{"Stage mapping matches Won?"}
  queue[("Creation queue")]
  worker["Jira creation worker"]
  jira["Jira create-issue API"]
  links[("Deal–issue links")]
  ignored["No action"]

  source -->|deal.updated| receiver
  receiver -->|Validated event| matcher
  matcher -->|Yes: enqueue creation| queue
  matcher -->|No: stop| ignored
  queue -->|Creation job| worker
  worker -->|Create issue| jira
  jira -->|Issue key| worker
  worker -->|Store deal ID and issue key| links
```