Advisory issues read as advice rather than failure

`ADVISORY_ISSUES` moves next to `ValidationIssue` in pipeline.py, and the
model derives an `advisory` flag from its own code, so the distinction the
engine already made ships to the client instead of being re-guessed there.

The dock keeps its summary in `--destructive` only when a real fault is
among the issues and paints an advisory row `--muted-foreground`; the
canvas leaves advisories off a node's dot and border entirely, since node
status has three colours and no warning tier.

biome checks the generated `openapi.json`, which nothing formats since the
SDK script dropped its format pass — ignore it like the other generated
files.

backend/tests/flow/test_pipeline.py

@@ -4,7 +4,7 @@ from fluksio.flow.controller import _declared_inputs
 from fluksio.flow.events import EventBus
 from fluksio.flow.messages import DType, MessageSpec
 from fluksio.flow.nodes import Node
-from fluksio.flow.pipeline import Pipeline
+from fluksio.flow.pipeline import Pipeline, ValidationIssue
 from fluksio.flow.schemas import FlowDef, FlowInput
 
 
@@ -197,3 +197,12 @@ def test_values_carry_timestamps():
     values = pipeline.values("f")
     assert values["f.out"]["value"] == 1.0
     assert values["f.out"]["ts"] > 0
+
+
+def test_only_advisory_codes_are_flagged_advisory():
+    """The UI reads this to keep an advisory out of the fault tone."""
+    hook = ValidationIssue(code="unauthenticated_hook", message="open")
+    cycle = ValidationIssue(code="cycle", message="loop")
+
+    assert hook.advisory is True
+    assert cycle.advisory is False