feat(auto-close): implement richer syntax support

AGENTS.md

@@ -527,13 +527,36 @@ result.frontmatter // Record<string, any>
 result.meta        // Record<string, any>
 ```
 
-### autoCloseMarkdown(markdown)
+### autoCloseMarkdown(markdown, options?)
+
+Self-healing markdown for streaming. Heals incomplete CommonMark/GFM per
+`packages/comark/SPEC/auto-close.md`, then completes Comark components / tables / frontmatter.
 
 ```typescript
 autoCloseMarkdown('**bold text')     // '**bold text**'
 autoCloseMarkdown('::alert\nContent') // '::alert\nContent\n::'
+
+// Incomplete links get a safe placeholder URL (default protocol mode)
+autoCloseMarkdown('[partial')
+// '[partial](comark:incomplete-link)'
+
+// Math (inline `$` and block `$$`) is off by default on bare autoCloseMarkdown
+autoCloseMarkdown('$x = 5') // '$x = 5'
+autoCloseMarkdown('$x = 5', { math: true }) // '$x = 5$'
+// parseMarkdown / createMarkdownParser pass math: true when math plugin provided
+
+// Plain markdown without Comark component fences
+autoCloseMarkdown('**bold', { syntax: false })
+
+// Streaming: drop a half-typed opener after whitespace so it does not flash
+autoCloseMarkdown('hello *', { dropTrailingOpeners: true }) // 'hello'
 ```
 
+Key options: `linkMode: 'protocol' | 'text-only'`, `math` (default false; on in parse),
+`dropTrailingOpeners` (default false; on when parsing with `streaming: true`),
+`incompleteLinkPlaceholder`, `incompleteImagePlaceholder`, `frontmatter`, `syntax`, `attributes`.
+Behavioral SPEC: `packages/comark/SPEC/auto-close.md` (run via `test/auto-close-spec.test.ts`).
+
 ## Markdown Document Model
 
 ```typescript

docs/content/5.reference/2.auto-close.md

@@ -14,14 +14,18 @@ links:
     variant: soft
 ---
 
-## `autoCloseMarkdown(source)`{lang="ts"}
+## `autoCloseMarkdown(source, options?)`{lang="ts"}
 
-Automatically closes unclosed markdown inline syntax and Comark components. Built for streaming scenarios where content arrives incrementally and may be incomplete at any point.
+Automatically closes unclosed markdown inline syntax and Comark components. Built for streaming scenarios where content arrives incrementally and may be incomplete at any point. CommonMark/GFM healing follows the behavioral SPEC in `packages/comark/SPEC/auto-close.md`.
 
 **Parameters:**
 
 - `source` - The markdown content (potentially partial/incomplete)
-- `options` (optional) - `frontmatter: true` completes an unclosed leading frontmatter block; `syntax: false` skips Comark component-fence closing (for content parsed without the components plugin)
+- `options` (optional) - Feature flags and Comark settings:
+  - **Comark:** `frontmatter: true` completes an unclosed leading frontmatter block; `syntax: false` skips component-fence closing; `attributes` controls `{...}` attribute scopes (defaults to `syntax`)
+  - **Links / images:** `linkMode: 'protocol' | 'text-only'` (default `'protocol'`), `incompleteLinkPlaceholder` (default `comark:incomplete-link`), `incompleteImagePlaceholder` (default `comark:incomplete-image`)
+  - **Math:** inline `$…$` and block `$$…$$` off by default on bare `autoCloseMarkdown`; pass `math: true` (or use `parseMarkdown`, which enables it)
+  - **Streaming:** `dropTrailingOpeners: true` drops a trailing opener after whitespace (`hello *` → `hello`) so half-typed markers do not flash. Enabled automatically when parsing with `streaming: true`.
 
 **Returns:** `string`, the source with all unclosed syntax closed
 
@@ -32,6 +36,19 @@ Automatically closes unclosed markdown inline syntax and Comark components. Buil
 import { autoCloseMarkdown } from 'comark'
 
 autoCloseMarkdown('**bold text')
+// '**bold text**'
+
+autoCloseMarkdown('[partial link')
+// '[partial link](comark:incomplete-link)'
+
+autoCloseMarkdown('$x = 5')
+// '$x = 5'
+
+autoCloseMarkdown('$x = 5', { math: true })
+// '$x = 5$'
+
+autoCloseMarkdown('hello *', { dropTrailingOpeners: true })
+// 'hello'
 ```
 
 ```typescript [Output]
@@ -79,11 +96,15 @@ const result = await parseMarkdown(closed, { autoClose: false })
 | Syntax | Example | Auto-closed |
 |--------|---------|-------------|
 | Bold | `**text` | `**text**` |
-| Italic | `*text` | `*text*` |
+| Italic | `*text` / `_text` | `*text*` / `_text_` |
+| Bold-italic | `***text` | `***text***` |
 | Code | `` `code `` | `` `code` `` |
 | Strikethrough | `~~text` | `~~text~~` |
-| Link | `[text](url` | `[text](url)` |
-| Image | `![alt](url` | `![alt](url)` |
+| Link (protocol) | `[text](url` | `[text](comark:incomplete-link)` |
+| Link (text-only) | `[text` | `text` |
+| Image | `![alt](url` | `![alt](comark:incomplete-image)` |
+| Block math | `$$x` | `$$x$$` |
+| Inline math | `$x` | `$x$` (`math: true`) |
 
 #### Comark components