feat(odt): conditionals for OpenDocument Text templates (#138)

[vaceslav]

Summary

Adds conditionals to OdtTemplateProcessor: {{#if}}, {{#elseif}}, {{#else}} and {{/if}}, with the full 1.7.0 condition engine. This is the second step of OpenDocument Text support.

Part of #138

Design

Follows docs/superpowers/specs/2026-09-26-odt-support-design.md (phase 2). The spec gains §8.1, which records the list decision below.

The ODT engine works like the Word pipeline:

• Conditionals are detected per block sequence and processed deepest first. Blocks already removed are skipped.
• Marker paragraphs are not processed for placeholders.
• Inline conditionals are resolved on the paragraph text with the shared InlineConditionalParser and ConditionalEvaluator. Only marker text and non-matching branch text is removed, and kept text retains its spans.
• Errors and warnings are the same as for DOCX: unmatched {{#if}}, {{#elseif}} after {{#else}}, several row markers in one row, and a malformed condition evaluates to false with an ExpressionFailed warning. Messages are unchanged, and errors surface as a failed ProcessingResult.

Design decision (lists), made conservatively and documented in spec §8.1. In ODF, list items are nested containers, not paragraphs as in Word. So:

• Markers in their own list items work like table rows: marker items are removed, and the items between them are kept or removed as a whole.
• A list with a single item (LibreOffice's representation of a lone bullet between paragraphs) carries marker text at the enclosing level, so a one-item list can act as a block marker, as in Word.
• A marker inside a longer list must be matched within that list; otherwise processing fails with the usual "no matching {{/if}}" error.

Container integrity:

• Emptied cells, text boxes, notes and headers/footers get an empty text:p.
• An emptied list item is removed.
• Lists, tables and header-row groups left without items or rows are removed, since ODF requires at least one row per table.

Changes

• OpenDocument/OdtMarkerText: marker text of paragraphs, rows, cells, list items and single-item lists. Text boxes, notes and annotations are excluded.
• OpenDocument/OdtConditionalBlock, OdtConditionalDetector: block, table-row and list-item detection. This is a port of ConditionalDetector over XElement. A container that holds a complete conditional is not treated as a marker.
• OpenDocument/OdtConditionalProcessor: evaluates branches and resolves inline conditionals. This is the counterpart of ConditionalVisitor.
• OdtTemplateEngine: conditional step per block sequence, per row container (table, header rows, row groups) and per list, plus the container-integrity rules above.
• XML docs of OdtTemplateProcessor updated to describe what is now supported.

No DOCX file was touched.

Tests

• Odt/OdtConditionalTests: 31 test methods.
  • Block conditionals, true and false.
  • elseif chains, nested blocks, removed branches not reporting missing variables.
  • Tables and lists inside blocks; headings as markers.
  • Inline conditionals: with else, elseif and nesting, several per paragraph, split across spans (keeps formatting), with placeholders.
  • Operators (and, in, contains, not, is empty, grouping, exists), conditions containing text:s, malformed condition → warning.
  • Table-row conditionals: else, multi-column rows, cell-level blocks and inline conditionals, all rows removed → table removed, header-row group removed, two markers in one row → failure.
  • List-item conditionals: an emptied list is removed; single-item-list markers; single-item list with a complete inline conditional.
  • Sections, headers/footers, text boxes and footnotes.
  • Unmatched {{#if}} and {{#elseif}} after {{#else}} → failure; marker paragraphs removed with their other text, as in Word.
• LibreOffice round trip (Conditionals_RoundTripThroughLibreOffice): block, inline with span, table row and list items. All 4 LibreOffice tests passed locally on net8.0, net9.0 and net10.0 (LibreOffice 25, macOS).
• Full suite green: 1968 tests on each of net8, net9 and net10; Tools and Converter tests green.
• Checks run: CI-mode Release build, dotnet format --verify-no-changes.

Public API impact: additive

No new public symbols. OdtTemplateProcessor (unreleased, added in #210) now evaluates conditionals, and its XML docs describe this. PublicAPI.Shipped.txt and PublicAPI.Unshipped.txt are unchanged.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 87.31884% with 35 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ev.Templify/OpenDocument/OdtConditionalDetector.cs	86.36%	11 Missing and 7 partials ⚠️
...riasDev.Templify/OpenDocument/OdtTemplateEngine.cs	84.12%	3 Missing and 7 partials ⚠️
...v.Templify/OpenDocument/OdtConditionalProcessor.cs	88.63%	0 Missing and 5 partials ⚠️
...asDev.Templify/OpenDocument/OdtConditionalBlock.cs	94.11%	1 Missing ⚠️
TriasDev.Templify/OpenDocument/OdtMarkerText.cs	95.00%	0 Missing and 1 partial ⚠️

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