feat(nav): ← Back to Home link on every tool page

Multi-file workflow: a user uploads several files on Home, clicks
"Open <Tool>" on one file's findings, lands on a tool page. The
sidebar lets them get back to Home, but a top-of-page back affordance
is more discoverable and keeps the hand in the same screen region as
the upload list they're working through.

- New ``back_to_home_link()`` helper in components/_legacy.py renders
  a secondary button that calls ``st.switch_page("app.py")`` — under
  ``st.navigation`` that routes to the default (Home) page.
- Wired into every tool page (1-9) directly after
  ``hide_streamlit_chrome()`` and BEFORE the license gate so a Lite
  user who lands on a locked tool can navigate away without paying.
- New i18n key ``nav.back_to_home`` ("← Back to Home" /
  "← Volver al inicio") in en/es packs.

2008 tests pass.

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

src/gui/components/__init__.py

@@ -46,6 +46,7 @@ from .activation import (  # noqa: F401  re-exported
 
 __all__ = [
     # Shared chrome / pickup
+    "back_to_home_link",
     "hide_streamlit_chrome",
     "shutdown_app",
     "pickup_or_upload",

src/gui/components/_legacy.py

@@ -187,6 +187,25 @@ def _farewell_script() -> str:
     )
 
 
+def back_to_home_link(*, key: str = "_back_to_home_link") -> None:
+    """Render a small "← Back to Home" affordance near the top of a tool page.
+
+    Tool pages reached from the home findings panel benefit from an
+    explicit return-to-home control so a user working through findings
+    on multiple uploaded files can hop between files without hunting
+    through the sidebar.
+
+    Implementation note: ``st.switch_page("app.py")`` routes back to the
+    entry script which, under ``st.navigation``, lands on the default
+    page (Home). Streamlit's button is used (rather than ``st.page_link``)
+    because the entry script is a navigation manager, not a registered
+    Page object, and ``page_link`` to ``app.py`` renders inconsistently
+    across Streamlit minor versions.
+    """
+    if st.button(_t("nav.back_to_home"), key=key, type="secondary"):
+        st.switch_page("app.py")
+
+
 def shutdown_app() -> None:
     """Terminate the Streamlit server immediately, no confirm.
 

src/gui/pages/1_Deduplicator.py

@@ -18,6 +18,7 @@ from src.core.dedup import deduplicate, DeduplicationResult
 from src.core.io import read_file, list_sheets, detect_encoding, detect_delimiter
 from src.gui.components import (
     apply_review_decisions,
+    back_to_home_link,
     config_panel,
     hide_streamlit_chrome,
     match_group_card,
@@ -28,6 +29,7 @@ from src.gui.components import (
 from src.license import FeatureFlag
 
 hide_streamlit_chrome()
+back_to_home_link()
 require_feature_or_render_upgrade(FeatureFlag.DEDUPLICATOR)
 
 # ---------------------------------------------------------------------------

src/gui/pages/2_Text_Cleaner.py

@@ -15,6 +15,7 @@ if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
 from src.gui.components import (
+    back_to_home_link,
     hide_streamlit_chrome,
     pickup_or_upload,
     render_hidden_aware_preview,
@@ -30,6 +31,7 @@ from src.core.text_clean import (
 )
 
 hide_streamlit_chrome()
+back_to_home_link()
 require_feature_or_render_upgrade(FeatureFlag.TEXT_CLEANER)
 
 

src/gui/pages/3_Format_Standardizer.py

@@ -15,6 +15,7 @@ if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
 from src.gui.components import (
+    back_to_home_link,
     hide_streamlit_chrome,
     pickup_or_upload,
     require_feature_or_render_upgrade,
@@ -28,6 +29,7 @@ from src.core.format_standardize import (
 from src.license import FeatureFlag
 
 hide_streamlit_chrome()
+back_to_home_link()
 require_feature_or_render_upgrade(FeatureFlag.FORMAT_STANDARDIZER)
 
 

src/gui/pages/4_Missing_Values.py

@@ -15,6 +15,7 @@ if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
 from src.gui.components import (
+    back_to_home_link,
     hide_streamlit_chrome,
     pickup_or_upload,
     require_feature_or_render_upgrade,
@@ -29,6 +30,7 @@ from src.core.missing import (
 from src.license import FeatureFlag
 
 hide_streamlit_chrome()
+back_to_home_link()
 require_feature_or_render_upgrade(FeatureFlag.MISSING_HANDLER)
 
 

src/gui/pages/5_Column_Mapper.py

@@ -15,6 +15,7 @@ if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
 from src.gui.components import (
+    back_to_home_link,
     hide_streamlit_chrome,
     pickup_or_upload,
     require_feature_or_render_upgrade,
@@ -30,6 +31,7 @@ from src.core.column_mapper import (
 from src.license import FeatureFlag
 
 hide_streamlit_chrome()
+back_to_home_link()
 require_feature_or_render_upgrade(FeatureFlag.COLUMN_MAPPER)
 
 

src/gui/pages/6_Outlier_Detector.py

@@ -12,12 +12,14 @@ if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
 from src.gui.components import (
+    back_to_home_link,
     hide_streamlit_chrome,
     require_feature_or_render_upgrade,
 )
 from src.license import FeatureFlag
 
 hide_streamlit_chrome()
+back_to_home_link()
 require_feature_or_render_upgrade(FeatureFlag.OUTLIER_DETECTOR)
 
 # ---------------------------------------------------------------------------

src/gui/pages/7_Multi_File_Merger.py

@@ -12,12 +12,14 @@ if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
 from src.gui.components import (
+    back_to_home_link,
     hide_streamlit_chrome,
     require_feature_or_render_upgrade,
 )
 from src.license import FeatureFlag
 
 hide_streamlit_chrome()
+back_to_home_link()
 require_feature_or_render_upgrade(FeatureFlag.MULTI_FILE_MERGER)
 
 # ---------------------------------------------------------------------------

src/gui/pages/8_Validator_Reporter.py

@@ -12,12 +12,14 @@ if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
 from src.gui.components import (
+    back_to_home_link,
     hide_streamlit_chrome,
     require_feature_or_render_upgrade,
 )
 from src.license import FeatureFlag
 
 hide_streamlit_chrome()
+back_to_home_link()
 require_feature_or_render_upgrade(FeatureFlag.VALIDATOR_REPORTER)
 
 # ---------------------------------------------------------------------------

src/gui/pages/9_Pipeline_Runner.py

@@ -15,6 +15,7 @@ if str(_project_root) not in sys.path:
     sys.path.insert(0, str(_project_root))
 
 from src.gui.components import (
+    back_to_home_link,
     hide_streamlit_chrome,
     pickup_or_upload,
     require_feature_or_render_upgrade,
@@ -31,6 +32,7 @@ from src.core.pipeline import (
 from src.license import FeatureFlag
 
 hide_streamlit_chrome()
+back_to_home_link()
 require_feature_or_render_upgrade(FeatureFlag.PIPELINE_RUNNER)
 
 

src/i18n/packs/en.json

@@ -149,6 +149,7 @@
     "section_account": "Account",
     "activate_title": "Activate",
     "close_title": "Close",
-    "section_close": "Close"
+    "section_close": "Close",
+    "back_to_home": "← Back to Home"
   }
 }

src/i18n/packs/es.json

@@ -149,6 +149,7 @@
     "section_account": "Cuenta",
     "activate_title": "Activar",
     "close_title": "Cerrar",
-    "section_close": "Cerrar"
+    "section_close": "Cerrar",
+    "back_to_home": "← Volver al inicio"
   }
 }