v1.10.0 — Generated indexes for ODT

Generated indexes for ODT — the last remaining "Out of scope" README entry
("generated indexes and tables of contents") is now in scope. The ODT skill
ships placeholder inserters for the four ODF index types plus a marker script
for the alphabetical index, and an update_indexes.py that mirrors recalc.py
(ODS v0.6) to dispatch the LibreOffice headless refresh.

Added

• add_toc.py — text:table-of-content with configurable outline level (default 3).
• add_bibliography.py — text:bibliography with entry templates.
• add_illustration_index.py — text:illustration-index (or text:table-index for --sequence Table); covers Figure/Table/Equation/custom sequences.
• add_alphabetical_index.py + add_index_mark.py — alphabetical index container + point markers.
• update_indexes.py — soffice-driven refresh in an isolated temp profile; never touches the user's real LibreOffice profile.
• build_index_body_placeholder — new helper in odf_lib.odf_common's public API.
• validate_refs.py (ODT) — four new warn-checks for structurally empty indexes.

See CHANGELOG.md for the full release notes.