docs: document remaining md support items

Author: tylerdave

docs/Markdown Support.md

@@ -32,7 +32,7 @@ Rockgarden supports the superset of CommonMark, GFM (GitHub Flavored Markdown),
 | ------------------- | ----------------------- | ------ | ------------------ |
 | Tables              | `\| col \| col \|`      | ✅     | Via markdown-it-py |
 | Strikethrough       | `~~text~~`              | ✅     | Via markdown-it-py |
-| Task lists          | `- [ ]` and `- [x]`     | ✅     | Via markdown-it-py |
+| Task lists          | `- [ ]` and `- [x]`     | ❌     | Planned            |
 | Autolinks           | Bare URLs               | ✅     | Via markdown-it-py |
 | Syntax highlighting | ` ```python `           | ❌     | Planned            |
 | Footnotes           | `[^1]` and `[^1]: text` | ❌     | Planned            |

plans/features/markdown-support.md

@@ -0,0 +1,26 @@
+# Markdown Support Gaps
+
+Unimplemented features documented in `docs/Markdown Support.md`. Grouped by effort and dependency.
+
+## Needs `mdit-py-plugins` dependency
+
+These require adding `mdit-py-plugins` and enabling plugins in `render/markdown.py`.
+
+- **Footnotes** (`[^1]` / `[^1]: text`) — documented as Planned. Plugin: `footnote`.
+- **Task lists** (`- [ ]` / `- [x]`) — documented as ✅ but not actually rendering. The `gfm-like` preset comments claim support but checkboxes render as literal text. Plugin: `tasklists`.
+
+## Needs client-side JS library
+
+- **Syntax highlighting** (` ```python `) — code fences output `class="language-*"` but no colorization. Options: highlight.js (simpler, auto-detection) or Prism (lighter, explicit). Could also do build-time with Pygments.
+- **Mermaid diagrams** (` ```mermaid `) — render fenced mermaid blocks as diagrams. See `plans/features/mermaid.md` for full spec.
+- **Math rendering** — inline `$...$`, block `$$...$$`, and GFM ` ```math ` fences. Needs KaTeX (lighter, faster) or MathJax (broader LaTeX support) client-side, or a build-time renderer.
+
+## Needs preprocessing (Python)
+
+These need processing in `render/preprocessors.py` or similar, before markdown-it-py parsing.
+
+- **Highlights** (`==text==`) — wrap in `<mark>` tags. Straightforward regex replacement (with code block protection).
+- **Comment stripping** (`%% comment %%`) — strip Obsidian comments during build. Regex replacement.
+- **Inline tags** (`#tag`, `#parent/child`) — parse inline tags from content body, add to page metadata. Intersects with collections design.
+- **Inline fields** (`key:: value`) — Dataview-style metadata. Parse and expose in page data.
+- **Block references** (`[[Page#^block]]`) — requires block-level ID assignment and cross-page reference resolution. Most complex item here.