docs+code: rename tool labels everywhere

Sweep follow-up to 93e43fc. Display labels now consistent across docs,
landing pages, CLI output, code comments, docstrings, and test prose.
Five parallel surfaces touched:

- docs (EN + ES): README, USER-GUIDE, CLI-REFERENCE, and 11 internal
  design/planning docs
- landing pages: index + bookkeeper/revops/shopify-pet
- src: CLI module docstrings, _TOOL_DISPLAY dicts in cli_analyze.py
  and gui/components/_legacy.py, core module headers, every tool
  page's module docstring
- tests: class/method/module docstrings and section-header comments
- test-cases READMEs

Page slugs (1_Deduplicator etc.), tool_id strings (01_deduplicator
etc.), Python class names (TestDeduplicatorWorkflow, FeatureFlag.*),
URL paths, anchor IDs, CSS classes, and asset filenames were left
intact since they're code identifiers / structural references.

All 2033 tests pass.

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

tests/gui/test_advanced_panels.py

@@ -5,7 +5,7 @@ expander that houses every per-column / per-strategy knob. It's the
 densest single widget surface in the GUI, so a session-state key drift
 in there cascades into every dedup session.
 
-We exercise it via the Deduplicator page (rendering ``config_panel``
+We exercise it via the Find Duplicates page (rendering ``config_panel``
 in isolation requires a fake Streamlit context). The page provides
 the surrounding state; we poke widgets and verify their effects.
 """