refactor(ui): drop v16 legacy tab

Keep only the v24 (new) feedback tab and the title proofreading sandbox.
v16 prompts/pipelines stay in the repo but are no longer surfaced in
the UI. _v16_prompt resolution removed from app.py.

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

app.py

@@ -3,7 +3,6 @@
 Tabs:
   - v24 (new): solar-pro3 with FT + self-consistency × 2 + tool-calling
     judge. paragraph F1 47.04 (vs solar-pro2 prod_251231 mean 44.86).
-  - v16 (legacy): solar-pro3 with the 260408_v16 single-pass pipeline.
   - 제목 교열 (sandbox): solar-pro2 vs solar-pro3 side-by-side comparison
     for newspaper title proofreading (default prompt hidden in UI).
 """
@@ -28,7 +27,7 @@ _vocab_path = os.path.join(os.path.dirname(__file__), "data", "vocabulary.csv")
 vocabulary = load_vocabulary(_vocab_path)
 
 
-prompt_choices = list_prompts() or ["dev_260408_v16"]
+prompt_choices = list_prompts() or ["dev_260429_v24"]
 
 
 def _default_prompt(preferred_prefix: str, fallback: str) -> str:
@@ -38,7 +37,6 @@ def _default_prompt(preferred_prefix: str, fallback: str) -> str:
     return fallback
 
 
-_v16_prompt = _default_prompt("dev_260408_v16", prompt_choices[-1])
 _v24_prompt = _default_prompt("dev_260429_v24", "dev_260429_v24")
 
 with gr.Blocks(title="Chosun 교정교열 데모") as demo:
@@ -53,14 +51,6 @@ with gr.Blocks(title="Chosun 교정교열 데모") as demo:
                 elem_id_prefix="v24",
             )
 
-        with gr.Tab("v16 (legacy · 260408)"):
-            build_feedback_tab(
-                client=client,
-                vocabulary=vocabulary,
-                pipeline_config=("260408_v16", "solar-pro3", _v16_prompt),
-                elem_id_prefix="v16",
-            )
-
         with gr.Tab("제목 교열 (sandbox)"):
             build_title_proofread_tab(client=client)
 
@@ -72,7 +62,7 @@ with gr.Blocks(title="Chosun 교정교열 데모") as demo:
     document.addEventListener('keydown', (e) => {
         if (!((e.metaKey || e.ctrlKey) && e.key === 'Enter')) return;
         // Pick the run button on the *visible* tab (others' buttons are hidden).
-        const ids = ['title-proofread-run-btn', 'v24-run-btn', 'v16-run-btn'];
+        const ids = ['title-proofread-run-btn', 'v24-run-btn'];
         for (const id of ids) {
             const root = document.getElementById(id);
             if (!root) continue;