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/support/documents.json

@@ -0,0 +1,30 @@
+{
+  "prose_docx": {
+    "filename": "bimeh_havades.docx",
+    "why": "38 paragraphs, all Normal, no tables: the plain-prose path, and the proof that no heading is invented where the document declares none."
+  },
+  "list_docx": {
+    "filename": "طرح ها-عمروحوادث-14050220.docx",
+    "why": "109 paragraphs mixing Normal and List Paragraph: prose carrying list styling."
+  },
+  "table_docx": {
+    "filename": "شماره تماس معاونت و مدیریتها14050309.docx",
+    "why": "One 35x5 contact table, no body prose. A data table with a real header row and a vertically merged first column."
+  },
+  "mixed_docx": {
+    "filename": "شرایط عمومی بیمه حوادث اشخاص14041205.docx",
+    "why": "Prose interleaved with two tables: a 30x3 list of injury compensations with NO header row, and an 11x2 table that has one."
+  },
+  "layout_docx": {
+    "filename": "چت بات-مهندسی.docx",
+    "why": "A 3x2 layout table whose single merged cell holds an entire 77k-character sub-document across 738 paragraphs and 5 nested tables."
+  },
+  "qa_xlsx": {
+    "filename": "fire14050319.xlsx",
+    "why": "Two-column Q&A sheet (q/a) plus a dead second sheet."
+  },
+  "branches_xlsx": {
+    "filename": "مشخصات شعب 28 اردیبهشت 1405.xlsx",
+    "why": "Branch directory: a merged title row above a two-row-tall merged header, and a vertically merged province column spanning each province's branches."
+  }
+}

tests/support/documents.py

@@ -0,0 +1,52 @@
+"""Load real production documents as test fixtures.
+
+Real files rather than generated ones: a fixture built with the same
+understanding of the format that produced the parser cannot catch a wrong
+mental model -- it is wrong in the same way, so the test passes and production
+breaks. Every table shape this parser handles was found by reading these
+files, not by reasoning about what DOCX can contain.
+
+The documents live outside the repository so no customer-facing file enters
+git history. Point `TEST_DOCUMENTS_DIR` at the directory holding them; tests
+that need one skip when it is absent.
+
+These skips cover a missing *external input*, never a failing assertion -- but
+a machine without the directory does run a smaller suite than CI should.
+
+Filenames live in `documents.json` rather than in this module: they are mostly
+Persian, and Arabic letterforms in Python source are flagged as ambiguous with
+Latin lookalikes (RUF001). They are data, so they belong in a data file.
+"""
+
+import json
+import os
+from pathlib import Path
+
+import pytest
+
+DOCUMENTS_DIR = Path(
+    os.environ.get("TEST_DOCUMENTS_DIR", "~/Documents/asia_data_sample")
+).expanduser()
+
+_MANIFEST = json.loads((Path(__file__).parent / "documents.json").read_text("utf-8"))
+
+# Each entry is the only sample exercising some structure; `why` in the
+# manifest records what would go untested without it.
+PROSE_DOCX = _MANIFEST["prose_docx"]["filename"]
+LIST_DOCX = _MANIFEST["list_docx"]["filename"]
+TABLE_DOCX = _MANIFEST["table_docx"]["filename"]
+MIXED_DOCX = _MANIFEST["mixed_docx"]["filename"]
+LAYOUT_DOCX = _MANIFEST["layout_docx"]["filename"]
+QA_XLSX = _MANIFEST["qa_xlsx"]["filename"]
+BRANCHES_XLSX = _MANIFEST["branches_xlsx"]["filename"]
+
+
+def load_document(filename: str) -> bytes:
+    """Return a real document's bytes, skipping the test when it is unavailable."""
+    path = DOCUMENTS_DIR / filename
+    if not path.is_file():
+        pytest.skip(
+            f"{filename} not found in {DOCUMENTS_DIR}; "
+            f"set TEST_DOCUMENTS_DIR to the directory holding the sample documents"
+        )
+    return path.read_bytes()