v1.1.0 — Custom type remapping support

This release introduces custom type remapping support in the alerts-normalize filter.
You can now map one alert/callout type to another via frontmatter, giving you more control
over how alerts are translated to different output formats.

Example configuration:

alerts-normalize:
  out-format: pandoc-format
  custom-types:
    - info: note

v1.0.0: Complete architectural refactor with 10 output formats

Architecture

The filter was rewritten from scratch around a two-stage pipeline:

• Stage 1 — Normalize: each reader (normalize_github, normalize_div) converts its input format into a canonical intermediate div with kind, title, and collapse attributes. No output format knowledge needed.
• Stage 2 — Write: write_callout dispatches to the correct writer via a Writers table keyed by Container enum. Each writer only knows its own syntax.

This replaces the original single-function approach (make_div) that mixed reading, normalizing, and writing into one path with two hardcoded outputs. The new design makes adding a format a matter of adding one row to FormatDefaults and one writer function, with no changes to existing code.

Breaking changes

• Metadata key redesigned. The old boolean-flag form (quarto-format: true) is replaced by a clean string or nested map:

  # simple string — works on command line and in frontmatter
  alerts-normalize: pandoc-format
  
  # nested map — for additional options
  alerts-normalize:
    out-format: pandoc-format
    custom-types:
      - spoiler
      - exercise

Added

• 10 output formats: quarto-format, pandoc-format, pandoc-md, github-format, obsidian-format, mkdocs-format, myst-format, sphinx-format, hugo-format, docusaurus-format, vitepress-format.
• pandoc-md intermediate format: attribute-based div representation for round-trip pipelines between readable formats.
• Collapse support: [!NOTE]- (collapsed) and [!NOTE]+ (expanded) markers are normalized to collapse="true/false" and round-trip correctly through all readable formats. Write-only formats use their native collapse syntax (??? for MkDocs, dropdown for MyST, :::details for VitePress/Docusaurus).
• Inline title capture: > [!NOTE] My title extracts the title correctly from the marker line.
• Any casing accepted: [!NOTE], [!Note], [!note] all normalize identically.
• Quarto div normalizer: :::{.callout-*} divs are read and converted to the intermediate format, enabling Quarto → any format pipelines.
• Pandoc 3.9 / Sphinx normalizer: :::{.note} plain classed divs with optional .title child or title= attribute are recognized.
• Extended callout type whitelist: 25 built-in types covering all major ecosystems (Obsidian, MkDocs, MyST, Sphinx, VitePress).
• custom-types frontmatter option: add types beyond the built-in whitelist without modifying the filter.
• Quarto source roundtrip: quarto-format → pandoc-md → quarto-format verified to produce identical output.
• Test metadata files updated to new out-format nested form.
• Dispatcher pattern: one write_callout entry point routes to the correct writer via a Writers table keyed by container type.

Changed

• Title handling mimics pandoc 3.9: the .title Div child is only inserted when the user explicitly sets a title. No auto-generation from the type name.
• write_blockquote produces pure AST objects — RawInline("markdown", ...) for the marker prevents Pandoc from escaping [ as \[, and BlockQuote wraps the content instead of RawBlock markdown text. Enables correct round-trip parsing.
• Format defaults extracted into a FormatDefaults table — no more if/elseif chain.
• Magic strings replaced by TypeCase and Container enums with runtime error protection against typos.