A run says whether the dashboard, the CLI or a script asked for it

`POST /runs/flows/{name}` hardcoded `cause: "api"`, so every row in the
history claimed the same origin. The body now carries an optional `cause`,
closed to the values the column knows — the dashboard sends nothing and stays
"api", `fluksio run` says "cli", and the SDK client says "sdk".

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013Gf7WaExcJ9bs3kfJXB3nK

backend/tests/api/routes/test_runs.py

@@ -311,6 +311,44 @@ def test_a_running_run_reports_how_long_it_has_been_going(
     assert rows[0]["duration_ms"] >= 30_000
 
 
+def test_a_run_records_which_caller_asked_for_it(
+    client, superuser_token_headers, monkeypatch
+):
+    """The dashboard, the CLI and the SDK are told apart by what they send.
+
+    Client-supplied, so the vocabulary is closed: a column nobody can write
+    free text into is one a table can group by.
+    """
+    seen: dict[str, object] = {}
+
+    class Recorder:
+        def submit(self, name, **kwargs):
+            seen.update(kwargs)
+            return Run(
+                id="cause-1",
+                flow=name,
+                cause=str(kwargs["cause"]),
+                created_at=datetime.now(UTC),
+            )
+
+    monkeypatch.setattr(client.app.state, "run_service", Recorder())
+    url = f"{settings.API_V1_STR}/runs/flows/demo"
+
+    answer = client.post(url, headers=superuser_token_headers, json={"cause": "cli"})
+    assert answer.status_code == 202
+    assert (seen["cause"], answer.json()["cause"]) == ("cli", "cli")
+
+    # Nothing said still means the dashboard, which is the only caller that
+    # does not name itself.
+    client.post(url, headers=superuser_token_headers, json={})
+    assert seen["cause"] == "api"
+
+    refused = client.post(
+        url, headers=superuser_token_headers, json={"cause": "somewhere else"}
+    )
+    assert refused.status_code == 422
+
+
 def test_overview_is_not_read_as_a_run_id(client, superuser_token_headers):
     """`/overview` is declared before `/{run_id}`, which would swallow it."""
     answer = client.get(