feat(onboarding): parakeet-as-default pinned by test; FirstRunPage handles distil ids

Parakeet-TDT scores 85 on any GPU-equipped English-capable system (Instant
speed + Great accuracy + GPU boost + headroom) vs ~75 for the best distilled
Whisper. A new test in recommendation.rs locks this in so future scoring
tweaks don't silently regress it.

FirstRunPage previously stored settings.modelSize by title-casing a lowercased
alias — which worked for Tiny/Base/Small/Medium but produced
"Whisper-distil-small-en" for the new distil ids. Swap to an id→label map
and pass the raw model id through to download_model/load_model; the backend
already accepts full ids via the whisper_model_id fallback.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/core/src/recommendation.rs

@@ -177,4 +177,19 @@ mod tests {
 
         assert!(ranked.is_empty());
     }
+
+    #[test]
+    fn parakeet_is_top_recommendation_when_hardware_supports_it() {
+        // Any machine that fits Parakeet in RAM should see it ranked first —
+        // Parakeet-TDT is English-only but beats Whisper on English at lower
+        // latency, so it's Kon's default recommendation when eligible.
+        // (Users on non-English languages adjust manually — handled at the
+        // settings-UI level, not at the scoring level for now.)
+        let profile = profile_with_ram(Megabytes(16384));
+
+        let ranked = rank_recommendations(&profile);
+        let top = ranked.first().expect("at least one model ranks");
+
+        assert_eq!(top.entry.engine, Engine::Parakeet);
+    }
 }