feat: hide Streamlit chrome for app-like appearance

Add shared hide_streamlit_chrome() helper that removes header bar,
hamburger menu, footer, and deploy button via CSS injection. Called
on every page. Add .streamlit/config.toml with minimal toolbar mode.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.streamlit/config.toml

@@ -0,0 +1,8 @@
+[client]
+toolbarMode = "minimal"
+
+[server]
+headless = true
+
+[browser]
+gatherUsageStats = false

src/gui/app.py

@@ -21,17 +21,15 @@ if str(_project_root) not in sys.path:
 # Page config
 # ---------------------------------------------------------------------------
 
+from src.gui.components import hide_streamlit_chrome
+
 st.set_page_config(
     page_title="DataTools — Data Cleaning Mastery",
     page_icon="🧹",
     layout="wide",
 )
 
-# Hide the Deploy button from the toolbar
-st.markdown(
-    "<style>[data-testid='stAppDeployButton'] {display: none;}</style>",
-    unsafe_allow_html=True,
-)
+hide_streamlit_chrome()
 
 
 # ---------------------------------------------------------------------------

src/gui/components.py

@@ -1,4 +1,4 @@
-"""Reusable Streamlit widgets for the deduplicator GUI."""
+"""Reusable Streamlit widgets for the DataTools GUI."""
 
 from __future__ import annotations
 
@@ -24,6 +24,45 @@ from src.core.config import (
 from src.core.normalizers import NormalizerType
 
 
+# ---------------------------------------------------------------------------
+# App chrome — hide Streamlit default UI for app-like feel
+# ---------------------------------------------------------------------------
+
+_HIDE_CHROME_CSS = """
+<style>
+/* Hide Streamlit header bar */
+header[data-testid="stHeader"] {
+    display: none !important;
+}
+/* Hide hamburger menu */
+button[kind="header"] {
+    display: none !important;
+}
+#MainMenu {
+    display: none !important;
+}
+/* Hide footer */
+footer {
+    display: none !important;
+}
+/* Hide deploy button */
+[data-testid="stAppDeployButton"] {
+    display: none !important;
+}
+/* Reclaim top padding lost from hidden header */
+.stAppViewBlockContainer,
+[data-testid="stAppViewBlockContainer"] {
+    padding-top: 1rem !important;
+}
+</style>
+"""
+
+
+def hide_streamlit_chrome() -> None:
+    """Inject CSS to hide Streamlit's default header, menu, and footer."""
+    st.markdown(_HIDE_CHROME_CSS, unsafe_allow_html=True)
+
+
 # ---------------------------------------------------------------------------
 # Config panel (advanced options)
 # ---------------------------------------------------------------------------

src/gui/pages/1_Deduplicator.py

@@ -19,10 +19,12 @@ from src.core.io import read_file, list_sheets, detect_encoding, detect_delimite
 from src.gui.components import (
     apply_review_decisions,
     config_panel,
+    hide_streamlit_chrome,
     match_group_card,
     results_summary,
 )
 
+hide_streamlit_chrome()
 
 # ---------------------------------------------------------------------------
 # Session state defaults

src/gui/pages/2_Text_Cleaner.py

@@ -11,6 +11,10 @@ _project_root = Path(__file__).resolve().parent.parent.parent.parent
 if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
+from src.gui.components import hide_streamlit_chrome
+
+hide_streamlit_chrome()
+
 # ---------------------------------------------------------------------------
 # Header
 # ---------------------------------------------------------------------------

src/gui/pages/3_Format_Standardizer.py

@@ -11,6 +11,10 @@ _project_root = Path(__file__).resolve().parent.parent.parent.parent
 if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
+from src.gui.components import hide_streamlit_chrome
+
+hide_streamlit_chrome()
+
 # ---------------------------------------------------------------------------
 # Header
 # ---------------------------------------------------------------------------

src/gui/pages/4_Missing_Values.py

@@ -11,6 +11,10 @@ _project_root = Path(__file__).resolve().parent.parent.parent.parent
 if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
+from src.gui.components import hide_streamlit_chrome
+
+hide_streamlit_chrome()
+
 # ---------------------------------------------------------------------------
 # Header
 # ---------------------------------------------------------------------------

src/gui/pages/5_Column_Mapper.py

@@ -11,6 +11,10 @@ _project_root = Path(__file__).resolve().parent.parent.parent.parent
 if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
+from src.gui.components import hide_streamlit_chrome
+
+hide_streamlit_chrome()
+
 # ---------------------------------------------------------------------------
 # Header
 # ---------------------------------------------------------------------------

src/gui/pages/6_Outlier_Detector.py

@@ -11,6 +11,10 @@ _project_root = Path(__file__).resolve().parent.parent.parent.parent
 if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
+from src.gui.components import hide_streamlit_chrome
+
+hide_streamlit_chrome()
+
 # ---------------------------------------------------------------------------
 # Header
 # ---------------------------------------------------------------------------

src/gui/pages/7_Multi_File_Merger.py

@@ -11,6 +11,10 @@ _project_root = Path(__file__).resolve().parent.parent.parent.parent
 if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
+from src.gui.components import hide_streamlit_chrome
+
+hide_streamlit_chrome()
+
 # ---------------------------------------------------------------------------
 # Header
 # ---------------------------------------------------------------------------

src/gui/pages/8_Validator_Reporter.py

@@ -11,6 +11,10 @@ _project_root = Path(__file__).resolve().parent.parent.parent.parent
 if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
+from src.gui.components import hide_streamlit_chrome
+
+hide_streamlit_chrome()
+
 # ---------------------------------------------------------------------------
 # Header
 # ---------------------------------------------------------------------------

src/gui/pages/9_Pipeline_Runner.py

@@ -11,6 +11,10 @@ _project_root = Path(__file__).resolve().parent.parent.parent.parent
 if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
+from src.gui.components import hide_streamlit_chrome
+
+hide_streamlit_chrome()
+
 # ---------------------------------------------------------------------------
 # Header
 # ---------------------------------------------------------------------------