Rebuilds the parsing layer for v1.0 on top of pypdfium2 (Apache-2.0 /
BSD-3) so casparser ships pure MIT end-to-end; the prior pdfminer.six
+ PyMuPDF dependencies are dropped along with the entire `casparser/
process/` regex-tokenisation pipeline they fed.

Engine (casparser/parsers/extract.py, pageobj.py)
=================================================

`extract.py` walks PDF page objects (one atom per text-show op),
maps glyphs to their parent atom via PDFium's
`FPDFText_GetTextObject`, deduplicates same-font overlapping atoms,
then emits `Char`/`Line`/`Page` shaped output that downstream
parsers consume. Atom-level dedup replaces all per-character
overlay heuristics: when two atoms share a font, x-overlap by
>=50% of the narrower atom's width, and sit 0.05-3.0pt apart in
y, we drop the one further from the row's median baseline. That
handles the date-twin artefact (same date column rendered twice
with a small y-offset, glyphs interleaving by x to produce garbage
like `2020 -> 22002200`) without the multi-stage sub-cluster
filters earlier prototypes used.

`pageobj.py` exposes the atoms + their column/block grouping that
the NSDL/CDSL parsers operate on directly. The same Atom primitive
backs the investor extractor.

Per-issuer parsers
==================

- `cams_detailed.py` / `cams_summary.py` consume the Line stream
  for CAMS + KFin DETAILED and SUMMARY templates.
- `nsdl.py` reads the page-2 account roster, walks per-account
  holdings sections (equities + mutual funds + corporate bonds in
  both summary and detailed forms). Section-aware routing handles
  the case where multiple holding types share the same 18-cell
  detailed table header by tracking `cur_section` from the
  preceding marker block. The page-2 roster accepts both the
  4-cell (broker + DP/Client joined) and 5-cell (broker, then
  DP/Client) variants.
- `cdsl.py` mirrors NSDL's structure for the CDSL CAS template.

Types
=====

- Adds `Bond` model with optional coupon_rate / coupon_frequency /
  maturity_date / face_value / market_price; required fields are
  isin, num_bonds, value. Surfaces on `DematAccount.bonds`.
- `investor_info` is now required on `CASData` and `NSDLCASData`.

Performance
===========

The dispatcher opens the PDF document exactly once per
`read_cas_pdf` call and threads the handle through detect /
parser / investor extractor via an `_doc=` kwarg. NSDL/CDSL
additionally share the extracted atoms between the holdings
parser and the investor extractor.

v0.9.0 shipped a PyMuPDF-1.25 compatibility fix on top of v0.8's
existing backend; v1.0 has already replaced that backend with
pypdfium2, so the v0.9 parser patches don't apply. The merge keeps
v1.0's parser layer and folds in the v0.9 metadata changes that
are still relevant:

- `casparser-isin>=2026.5.1` (DB format v2 with sebi_category /
  last_seen / ISIN-first lookup priority) — adopted.
- `pdfminer.six` and the `mupdf`/`fast` PyMuPDF extras stay
  removed (1.0.0's pure-pypdfium2 stack).
- `MutualFund.fix_float` aliased-field bug fix (v0.9 patched it
  on the v0.8 model; v1.0's model already carries the same fix).
- CI matrix: adopt v0.9's `[3.11, 3.12, 3.13]` Python matrix; drop
  `--all-extras` from `uv sync` (no extras to install any more).
- CHANGELOG keeps the 1.0.0 entry on top and a condensed 0.9.0
  entry below it for historical record.

Files v0.9 modified that v1.0 had already deleted are kept deleted:
- casparser/parsers/mupdf.py
- casparser/process/{__init__,cas_detailed,cas_summary,cdsl_statement,
  nsdl_statement,regex,utils}.py

Tests: 151/151 with private fixtures, 87/87 + 64 skipped without.