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.

docs/adr/0004-docx-csv-chunking-strategy.md

@@ -4,6 +4,23 @@
 
 Accepted
 
+> Amended by
+> [ADR-0018](0018-docx-and-spreadsheet-parsing-with-fixed-size-chunking.md):
+> v1 ships **fixed-size** chunking rather than the semantic-aware default
+> below, and defers `qa_pair` detection and image captioning. Docx tables do
+> become `table_row` units as this ADR specifies, but only when they are data:
+> a table holding a cell larger than one chunk, or a cell containing nested
+> tables, is treated as page layout and its cells are chunked as prose.
+> Row labels are applied only when row 0 is provably a header, and cells are
+> joined unlabeled otherwise. No document tree is built, and no heading is
+> inferred from text. `.doc` is rejected with `415` pending an out-of-process
+> conversion service rather than shelling out to LibreOffice. ADR-0018 also
+> adds a Persian normalization step at parse time and fixes the chunk-size
+> numbers this ADR left open. The spreadsheet row-to-chunk rules, the
+> embedding model, the task-prefix invariant, and the `content_type` value set
+> below all apply unchanged — except that `.csv` is read with the standard
+> library `csv` module rather than `pandas`.
+
 ## Context
 
 ADR-0001 deferred two things to "when we start the docx/csv chunking work":