fix(dashboard): surface model-write failure when creating a profile

[AhmetArif0]

Problem

POST /api/profiles returns model_set: false when the profile is created successfully but the follow-up model assignment step fails (e.g. filesystem error writing config.yaml). handleCreate on the Profiles page discarded the entire response with a bare await:

await api.createProfile({ ..., provider: picked?.provider, model: picked?.model });
showToast(`${t.profiles.created}: ${name}`, "success");

The user sees a "Profile created" success toast with no indication that their chosen model was not persisted. They then need to discover the mismatch themselves from the profile editor.

Fix

Capture the response and show a follow-up error toast when the user explicitly selected a model (picked is truthy) but res.model_set came back false:

const res = await api.createProfile({ ... });
showToast(`${t.profiles.created}: ${name}`, "success");
if (picked && res.model_set === false) {
  showToast(
    `Profile created, but the model could not be saved — set it from the profile editor.`,
    "error",
  );
}

Strict === false means the warning is silently skipped when model_set is undefined (older server that predates the field), keeping backwards compatibility.

Test plan

• Create a profile with a model selected, backend write succeeds → only success toast shown
• Simulate model write failure (e.g. make the profile config.yaml read-only) → success toast followed by the model-failure error toast
• Create a profile with no model selected → only success toast, no model warning regardless of model_set

[teknium1]

Merged via PR #39070. Your commit was cherry-picked onto current main as c2d11cc with your authorship preserved in git log. Thanks!