feat(ingestion): add DOCX/CSV/XLSX parsing and fixed-size chunking (ADR-0018)

Adds src/application/ingestion/ -- Persian normalization, DOCX body
walk with structural data/layout table classification, CSV/XLSX row
rendering, and fixed-size token chunking (cl100k_base, 400/60/512) --
as pure functions per ADR-0015, tested against real production
documents (asia_data_sample, kept out of the repo). ADR-0018 records
where this diverges from ADR-0004 (fixed-size default, no invented
headings/tree, structural table classification, header-provable
labeling only). Plan 001's scope line is corrected from CSV-only to
DOCX/XLSX/CSV, and CLAUDE.md's stale project-status paragraph is
updated to match current implementation state.

tests/unit/application/test_normalization.py

@@ -0,0 +1,95 @@
+"""Persian normalization (ADR-0018).
+
+Characters are written as escapes rather than literals: Arabic letterforms are
+visually indistinguishable in a monospace editor, and literals would render
+right-to-left and visually reorder each assertion.
+"""
+
+import pytest
+
+from src.application.ingestion import normalize_persian_text
+
+pytestmark = pytest.mark.unit
+
+ARABIC_KAF = chr(0x0643)
+PERSIAN_KEHEH = chr(0x06A9)
+ARABIC_YEH = chr(0x064A)
+ALEF_MAKSURA = chr(0x0649)
+PERSIAN_YEH = chr(0x06CC)
+ALEF_HAMZA_ABOVE = chr(0x0623)
+ALEF_HAMZA_BELOW = chr(0x0625)
+ALEF = chr(0x0627)
+ALEF_FINAL_FORM = chr(0xFE8E)
+
+FATHA = chr(0x064E)
+SHADDA = chr(0x0651)
+TATWEEL = chr(0x0640)
+SUPERSCRIPT_ALEF = chr(0x0670)
+
+PERSIAN_DIGITS = "".join(chr(0x06F1 + offset) for offset in range(3))
+ARABIC_SEMICOLON = chr(0x061B)
+ARABIC_THOUSANDS_SEPARATOR = chr(0x066C)
+
+
+@pytest.mark.parametrize(
+    ("source", "expected"),
+    [
+        (ARABIC_KAF, PERSIAN_KEHEH),
+        (ARABIC_YEH, PERSIAN_YEH),
+        (ALEF_MAKSURA, PERSIAN_YEH),
+        (ALEF_HAMZA_ABOVE, ALEF),
+        (ALEF_HAMZA_BELOW, ALEF),
+    ],
+)
+def test_normalize_arabic_letterform_folds_to_persian(source: str, expected: str) -> None:
+    assert normalize_persian_text(source) == expected
+
+
+def test_normalize_mixed_keyboard_spellings_converge_to_one_form() -> None:
+    """The defect this module exists for: one word, two spellings, two embeddings."""
+    arabic_spelling = f"{ARABIC_KAF}{ARABIC_YEH}"
+    persian_spelling = f"{PERSIAN_KEHEH}{PERSIAN_YEH}"
+
+    assert normalize_persian_text(arabic_spelling) == normalize_persian_text(persian_spelling)
+
+
+@pytest.mark.parametrize("mark", [FATHA, SHADDA, TATWEEL, SUPERSCRIPT_ALEF])
+def test_normalize_diacritic_is_removed(mark: str) -> None:
+    assert normalize_persian_text(f"{ALEF}{mark}{ALEF}") == f"{ALEF}{ALEF}"
+
+
+def test_normalize_not_sign_becomes_space() -> None:
+    assert normalize_persian_text(f"{ALEF}¬{ALEF}") == f"{ALEF} {ALEF}"
+
+
+def test_normalize_applies_nfkc_compatibility_forms() -> None:
+    # U+FE8E is the final presentation form of alef; NFKC maps it to the base
+    # letter, so a document pasted from a PDF renderer matches a typed one.
+    assert normalize_persian_text(ALEF_FINAL_FORM) == ALEF
+
+
+def test_normalize_collapses_whitespace_runs_and_strips() -> None:
+    assert normalize_persian_text("  a \t\n  b  ") == "a b"
+
+
+@pytest.mark.parametrize(
+    "preserved",
+    [PERSIAN_DIGITS, ARABIC_SEMICOLON, ARABIC_THOUSANDS_SEPARATOR],
+)
+def test_normalize_digits_and_punctuation_survive_unchanged(preserved: str) -> None:
+    """ADR-0018 deliberately folds letters only.
+
+    Rewriting Persian digits to Western ones would render citations wrong to a
+    Persian reader, so this guards against a later 'helpful' addition.
+    """
+    assert normalize_persian_text(preserved) == preserved
+
+
+def test_normalize_already_normalized_text_is_unchanged() -> None:
+    normalized = normalize_persian_text(f"{ARABIC_KAF}{FATHA} {ALEF_HAMZA_ABOVE}")
+
+    assert normalize_persian_text(normalized) == normalized
+
+
+def test_normalize_empty_string_returns_empty() -> None:
+    assert normalize_persian_text("") == ""