docs: OpenDocument (LibreOffice) support documentation and examples (#138)

[vaceslav]

Summary

Documentation and examples for OpenDocument Text (.odt/.ott) support: OdtTemplateProcessor (#210–#214) and the format-detecting TemplateProcessor facade (#215).

Changes

• New docs pages (both in the mkdocs nav):
  • docs/for-template-authors/libreoffice.md ("LibreOffice / OpenDocument"). It covers authoring templates in LibreOffice Writer (saving as .odt/.ott, AutoCorrect quotes, no .fodt) and what is supported, including the list rules. It also covers the differences from Word, taken from the spec's known gaps: whitespace collapsing, row spans not adjusted, bookmarks not renamed, UpdateFieldsOnOpen not applicable, comments not processed, signatures removed, encrypted files rejected, .fodt unsupported.
  • docs/for-developers/opendocument.md ("OpenDocument (.odt)"). It covers the OdtTemplateProcessor API (files, bytes, a write-only output stream, .ott → .odt, options and DocumentProperties → meta.xml, validation) and the TemplateProcessor facade (detection rules, DetectFormat, stream behavior, unsupported formats).
• Links from docs/index.md, the FAQ ("Can I write templates in LibreOffice?") and Getting Started.
• READMEs: the root README has the tagline, the key feature and a "LibreOffice / OpenDocument Templates" quick sample. The NuGet readme (TriasDev.Templify/README.md) has the headline, the feature bullet and a sample with both processors and DetectFormat.
• Package metadata: the Description mentions .odt/.ott and LibreOffice (and drops the outdated "100% test coverage" claim). Tags odt, ott, opendocument and libreoffice are added.
• CLAUDE.md: an "OpenDocument (.odt / .ott)" architecture section (engine, package, facade, known gaps, tests in TriasDev.Templify.Tests/Odt/), the code organization and test locations, the markdown note, and updated test counts.
• ARCHITECTURE.md: a short "OpenDocument Text" section with the processing flow and the reused components, plus a source layout row.
• DocumentGenerator: a new libreoffice-letter example. It writes an .odt package directly (fixed entry order and timestamps, so the output is deterministic) and processes it with the facade. It covers placeholders, a date format, markdown, if/else around paragraphs and a bulleted list, a list-item loop, a table-row loop with a header row, and a footer placeholder. examples/templates/libreoffice-letter-template.odt and examples/outputs/libreoffice-letter-output.odt are committed. I checked the output with LibreOffice 25 headless (txt and pdf): it renders correctly, with the footer, bold/italic markdown, bullets and table. The example READMEs are updated.
• Demo: the custom mode (--template x --data y.json) now uses TemplateProcessor, so --template x.odt/.ott works. The default output extension follows the detected format, and an unsupported file is rejected with a clear message.

Tests

• TriasDev.Templify.Tests/Documentation/OpenDocumentSamplesTests.cs has 13 tests that mirror every sample and documented behavior on the new pages and README sections: file to file, .ott → .odt, bytes plus File.OpenWrite, a Word template given to the ODT processor, DocumentProperties in meta.xml, validation, the facade for docx/odt/ott, DetectFormat and position restore, an unsupported .fodt, typographic quotes, list-item loops, and an unmatched marker in a longer list.
• Tools.Tests ExampleGeneratorSmokeTests: all generators are processed through the facade (the text reader handles ODT). There is a new theory that validates every generator's template with its sample data. It relies on the fix in fix(odt): ValidateTemplate no longer reports the markers of table-row and list-item blocks as unmatched (#138) #216, which this PR found. The PR also adds a content test and a determinism test for libreoffice-letter.
• Local checks: the Release CI build passed. Core has 2091 tests per TFM (net10/9/8, including the LibreOffice round trips), Tools 52 and Converter 95. dotnet format --verify-no-changes, dotnet pack (package validation) and mkdocs build --strict passed.

Public API impact

None. This PR changes docs, examples, tools and package metadata only.

Refs #138

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 93.57143% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...Generator/Generators/LibreOfficeLetterGenerator.cs	94.89%	4 Missing and 3 partials ⚠️
TriasDev.Templify.DocumentGenerator/Program.cs	0.00%	2 Missing ⚠️

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