feat: 3 new tools, format streaming, distribution-ready demo + landing pages

Tools shipped this batch (4 → 6 of 9 Ready):
  04 Missing Value Handler   src/core/missing.py + cli_missing.py + GUI
  05 Column Mapper           src/core/column_mapper.py + cli_column_map.py + GUI
  09 Pipeline Runner         src/core/pipeline.py + cli_pipeline.py + GUI
                             with soft tool-dependency graph (recommended,
                             not enforced) and JSON save/load for repeatable
                             weekly cleanups.

Format Standardizer reworked for 1 GB international files:
  • Vectorised dispatch + LRU cache over phone/date/currency/boolean/email
  • Per-row country / address columns drive parsing
  • Audit cap (default 10 k rows, ~50 MB RAM)
  • standardize_file(): chunked streaming entry point (~165 k rows/sec)
  • currency_decimal="auto" for EU comma-decimal locales
  • R$ / kr / zł multi-char currency prefixes
  • cli_format.py with auto-stream above 100 MB inputs

Encoding detection arbiter + language-aware probe:
  Closes the last 4 xfails (cp1250 / mac_iceland / shift_jis_2004 / lying-BOM)
  via tied-confidence arbiter + Cyrillic / EE-Latin coverage probes.

Distribution-readiness assets:
  • streamlit_app.py — Streamlit Community Cloud entry shim
  • src/gui/app_demo.py — single-page demo, ?p=<persona> routing,
    100-row cap + watermark, free-vs-paid boundary enforced at surface
  • samples/demo/ — 3 niche datasets + pre-tuned pipeline JSONs
  • landing/ — 4 static HTML pages (apex chooser + 3 niche),
    shared CSS, deploy.py URL-substitution script,
    auto-generated robots.txt + sitemap.xml + 404.html + favicon
  • docs/PLAN.md, DEMO-PLAN.md, DEPLOYMENT.md, POST-LAUNCH.md, NEXT-STEPS.md
    — full strategy + measurement + deployment + master checklist

Test counts:
  before: 1,520 passed · 4 skipped · 17 xfailed
  after:  1,729 passed · 0 skipped · 0  xfailed

Tier-1 corpora added:
  • missing-corpus           3 use cases + 16 edge cases
  • column-mapper-corpus     3 use cases + 5 edge cases
  • format-cleaner intl      20-row 13-country stress fixture

Engine hardening flushed out by the corpora:
  • interpolate guards against object-dtype columns
  • mean/median skip all-NaN columns (silences numpy warning)
  • fillna runs under future.no_silent_downcasting (silences pandas warning)
  • mojibake test no longer skips when ftfy installed (monkeypatch path)
  • drop-row threshold semantics: strict-greater (consistent across rows / cols)
  • currency_decimal validator allow-set updated for "auto"

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

tests/test_corpus.py

@@ -169,8 +169,23 @@ class TestMojibake:
         assert actual.equals(expected), "14 mojibake default (no repair) differs"
 
     def test_fixed_variant(self):
-        # --fix-mojibake is Tier 2; the cleaner does not implement it. Mark xfail.
-        pytest.xfail("Mojibake auto-repair is Tier 2; not yet implemented (uses ftfy).")
+        """Mojibake auto-repair (ftfy-backed) restores the original text.
+
+        Skipped automatically when ftfy is not installed — the engine
+        falls back to a no-op in that case and the diff would never close.
+        """
+        try:
+            import ftfy  # noqa: F401
+        except ImportError:
+            pytest.skip("ftfy not installed — install ftfy to enable mojibake repair")
+
+        from src.core.fixes import repair_mojibake
+
+        df = _read_csv_strict(TEST_DATA / "14_mojibake.csv")
+        expected = _read_csv_strict(EXPECTED / "14_mojibake__fixed.csv")
+        repaired, _ = repair_mojibake(df)
+        actual = repaired.reset_index(drop=True)
+        assert actual.equals(expected), "14 mojibake fixed variant differs"
 
 
 class TestEmptyFile: