* feat(plugins): add sectioned long-form report writing example
A standalone example extension whose save_section model tool stores a
万字-scale report section by section (SQLite, per-user and per-thread)
and assembles every section into one markdown document on a final
section_index=999 call. The assembled document is returned as a tool
artifact with only a short status line re-entering the model context, so
the full report never consumes the context budget.
Assembly drops a section's leading heading when it restates the section
title (models habitually open each section with '# <title>' while the
assembler already emits '## <title>'), which otherwise doubles every
heading in the document. The outline section passes through unwrapped
and keeps its own heading as the document title.
* fix(frontend): register report sections in extension catalog
* docs(report-sections): correct the test command path
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Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
