T1-5: Emit DbtRunCompleted from tycoon data transform run

[JesuFemi-O]

Milestone: #82
Depends on: #91, #93

Context

src/tycoon/commands/transform.py _capture_dbt_and_refresh_safe() is called after every dbt invocation. It currently calls observability.capture_dbt_safe() and capture_dbt_manifest_safe(). dbt writes its run results to dbt_project_dir / "target" / "run_results.json" after every invocation.

Goal

At the end of _capture_dbt_and_refresh_safe(), after the existing calls, read run_results.json (if present) and append a DbtRunCompleted event. The JSON structure is:

{
  "elapsed_time": 4.23,
  "results": [
    {"status": "success"},
    {"status": "error"}
  ]
}

Build the event:

results = data.get("results", [])
event = DbtRunCompleted(
    source_id="dbt",
    runtime_id="dbt",
    command=command,       # the dbt subcommand: "run", "build", "test"
    target=resolved_target,
    models_run=len(results),
    models_passed=sum(1 for r in results if r.get("status") == "success"),
    models_errored=sum(1 for r in results if r.get("status") == "error"),
    duration_seconds=data.get("elapsed_time", 0.0),
)

Wrap in try/except Exception: pass.

Acceptance

After tycoon data transform run, running the DuckDB query from #95 shows a dbt_run_completed event.

[JesuFemi-O]

Implemented in PR #137 (merged 2026-07-15). _capture_dbt_and_refresh_safe in src/tycoon/commands/transform.py reads run_results.json after each dbt subprocess and appends a DbtRunCompleted event to the metadata backend. Includes mtime guard to prevent stale-file emission on crash.