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_gate.py

@@ -11,7 +11,7 @@ exist, each pinned here:
 3. **Upload + matching passed normalization** — gate is a no-op; the
    page proceeds.
 
-We exercise the gate via the Deduplicator page (any tool page would
+We exercise the gate via the Find Duplicates page (any tool page would
 work; dedup is the smallest one that doesn't depend on heavy widgets).
 """
 
@@ -27,7 +27,7 @@ from .conftest import (
 )
 
 
-# Deduplicator is our canary — it calls ``require_normalization_gate``
+# Find Duplicates is our canary — it calls ``require_normalization_gate``
 # on the second line of the module. If the gate blocks, the dedup-
 # specific title shouldn't even render.
 GATED_PAGE = "1_Deduplicator"