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_analyze.py

@@ -253,16 +253,20 @@ class TestEncodingOverride:
 
 
 class TestEncodingDecodeFailedFromRepair:
-    def test_decode_replaced_action_surfaces_error_finding(self, tmp_path):
-        # Create a file with a UTF-8 BOM but cp1252 body bytes — utf-8-sig
-        # fails on byte 0x80 (€ in cp1252).
+    def test_lying_bom_recovered_and_flagged(self, tmp_path):
+        # File has a UTF-8 BOM but the body bytes are cp1252 (0x80 = € in
+        # cp1252; not a valid UTF-8 continuation byte). Detector should
+        # recover transparently to cp1252 and surface an
+        # ``encoding_lying_bom`` warn so the user knows.
         f = tmp_path / "lying_bom.csv"
         f.write_bytes(b"\xef\xbb\xbfid,name\n1,\x80100\n")
         findings = analyze(f)
         ids = {x.id for x in findings}
-        assert "encoding_decode_failed" in ids
-        bad = next(x for x in findings if x.id == "encoding_decode_failed")
-        assert bad.severity == "error"
+        assert "encoding_lying_bom" in ids
+        bad = next(x for x in findings if x.id == "encoding_lying_bom")
+        assert bad.severity == "warn"
+        # Decode should have succeeded — no replacement-character finding.
+        assert "encoding_decode_failed" not in ids
 
 
 class TestMixedLineEndings: