improvement(rich-markdown-editor): table column-resize cursor, exhaustive paste tests, editor docs (#5455)

* fix(rich-markdown-editor): show the col-resize cursor on table column borders

prosemirror-tables toggles a `resize-cursor` class on the editor while the pointer is over a
column boundary, but there was no rule to change the cursor — the blue resize handle showed with
no cursor affordance. Add the scoped `col-resize` rule.

* test(rich-markdown-editor): exhaustive markdown paste coverage

Cover every rich construct (headings, marks, lists, task lists, blockquote, code block, image,
thematic break, table), markdown parsed despite an HTML sibling, multi-block order, read-only
rejection, and the defer/verbatim cases for non-markdown input.

* docs(editor): add rich markdown editor page

Document the inline rich markdown editor — formatting, structure, lists, tables, code blocks,
images, the slash menu, and markdown fidelity — with a rendered overview screenshot.

* test(rich-markdown-editor): scope paste tests to what MarkdownPaste actually gates

Inline-only marks (single-asterisk italic, ~~, single-backtick code) are intentionally not detected
by looksLikeMarkdown (single `*` would false-positive on e.g. `*args`); they route through the
Markdown extension's own paste path, not MarkdownPaste. Move them from the rich-render cases to the
defers-to-default cases so the suite tests the handler it names.

apps/docs/content/docs/en/files/editor.mdx

@@ -0,0 +1,56 @@
+---
+title: Editor
+description: A rich markdown editor for your files — type markdown and watch it render, or edit visually.
+pageType: concept
+---
+
+import { Image } from '@/components/ui/image'
+import { Card, Cards } from 'fumadocs-ui/components/card'
+import { Callout } from 'fumadocs-ui/components/callout'
+
+Every markdown file in your workspace opens in a **rich editor**. Type markdown and it renders as you go, or format visually with the toolbar and slash menu. What you see is exactly what gets saved — plain markdown underneath, no lock-in.
+
+<div className="mx-auto w-full overflow-hidden rounded-lg my-6">
+  <Image src="/static/files/editor/overview.png" alt="A markdown file rendered in the editor: headings, bold, italic, and a link, a nested bullet list, and a table" width={900} height={410} />
+</div>
+
+## Formatting text
+
+Select any text to bring up the formatting toolbar — bold, italic, strikethrough, inline code, and links. The same marks appear instantly as you type the markdown for them, like `**bold**` or `*italic*`. Links show a hover card so you can open, copy, edit, or remove them without hunting through the source.
+
+## Structure
+
+Headings, blockquotes, and dividers keep long documents scannable. Type `# ` through `###### ` for headings, `> ` for a quote, and `---` for a divider.
+
+## Lists and checklists
+
+Bullet, ordered, and nested lists all work, plus task lists you can tick right in the document.
+
+## Tables
+
+Insert a table from the slash menu, then click any cell for the floating table toolbar — add or remove rows and columns, toggle the header row, or delete the table. Drag a column border to resize it.
+
+## Code blocks
+
+Fenced code blocks are syntax-highlighted, with a language picker in the corner. Pick `mermaid` to render a live diagram instead of code.
+
+## Images
+
+Paste or drag an image straight into the document, then drag a corner to resize it.
+
+## Slash menu and shortcuts
+
+Type `/` anywhere to insert any block — heading, list, table, code block, image, and more — without leaving the keyboard. Familiar shortcuts work too: **Cmd/Ctrl + B** for bold, **Cmd/Ctrl + I** for italic, and **Cmd/Ctrl + K** to add a link over selected text.
+
+## Markdown fidelity
+
+The editor round-trips your markdown exactly — it saves what you wrote, with no reformatting churn.
+
+<Callout type="info">
+A few constructs can't be represented visually without losing information on save — footnotes, raw HTML, and HTML comments. When a file contains one of these, it opens **read-only** so the original source is preserved untouched. Everything is still rendered faithfully; you just can't edit that file inline.
+</Callout>
+
+<Cards>
+  <Card title="Generating files" href="/files/generating" description="Have a workflow produce a document from a run." />
+  <Card title="Using files in workflows" href="/files/using-in-workflows" description="Read a file into a workflow and produce one from a run." />
+</Cards>

apps/docs/content/docs/en/meta.json

@@ -27,6 +27,7 @@
     "./tables/workflow-columns",
     "---Files---",
     "./files/index",
+    "./files/editor",
     "./files/using-in-workflows",
     "./files/generating",
     "./files/passing-files",

apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/rich-markdown-editor/markdown-paste.test.ts

@@ -16,8 +16,8 @@ afterEach(() => {
   editor = null
 })
 
-function mount(): Editor {
-  return new Editor({ extensions: [...createMarkdownContentExtensions(), MarkdownPaste] })
+function mount(editable = true): Editor {
+  return new Editor({ extensions: [...createMarkdownContentExtensions(), MarkdownPaste], editable })
 }
 
 /** Run the plugin paste handlers the way ProseMirror would, with a mocked clipboard. */
@@ -93,4 +93,61 @@ describe('markdown paste', () => {
     expect(editor.isActive('codeBlock')).toBe(true)
     expect(paste(editor, '[link](https://example.com)')).toBe(false)
   })
+
+  it('rejects the paste entirely in a read-only editor', () => {
+    editor = mount(false)
+    expect(paste(editor, '# heading\n\n- one\n- two')).toBe(false)
+    expect(editor.getText()).toBe('')
+  })
+
+  it.each([
+    ['empty string', ''],
+    ['whitespace only', '   \n\n  '],
+    ['a bare thematic break (ambiguous — needs another markdown signal)', '---'],
+    ['inline-only italic (single asterisk would false-positive on e.g. *args)', 'an *italic* word'],
+    ['inline-only strikethrough', 'a ~~struck~~ word'],
+    ['inline-only code', 'some `code` here'],
+  ])('leaves %s to the default handler', (_label, text) => {
+    editor = mount()
+    expect(paste(editor, text)).toBe(false)
+  })
+
+  // Only structural / unambiguous constructs gate the markdown parse. Inline-only marks that
+  // `looksLikeMarkdown` deliberately omits to avoid false positives — single-asterisk italic
+  // (`*args`), `~~`, single-backtick code — are covered by the Markdown extension's own paste path,
+  // not MarkdownPaste, so they belong to a different test surface.
+  it.each([
+    ['heading', '# Heading', 'heading'],
+    ['bold', 'a **bold** word', 'bold'],
+    ['bullet list', '- one\n- two', 'bulletList'],
+    ['ordered list', '1. one\n2. two', 'orderedList'],
+    ['task list', '- [x] done\n- [ ] todo', 'taskList'],
+    ['blockquote', '> a quote', 'blockquote'],
+    ['fenced code block', '```ts\nconst x = 1\n```', 'codeBlock'],
+    ['standalone image', '![alt](https://e.com/i.png)', 'image'],
+    ['thematic break within a document', '# Title\n\n---\n\nbody', 'horizontalRule'],
+  ])('renders pasted %s as rich content', (_label, md, nodeType) => {
+    editor = mount()
+    expect(paste(editor, md)).toBe(true)
+    expect(JSON.stringify(editor.getJSON())).toContain(`"type":"${nodeType}"`)
+  })
+
+  it('parses markdown-shaped plain text even when an HTML sibling is present', () => {
+    editor = mount()
+    const html = '<h1>Title</h1><ul><li>a</li><li>b</li></ul>'
+    expect(paste(editor, '# Title\n\n- a\n- b', html)).toBe(true)
+    const json = JSON.stringify(editor.getJSON())
+    expect(json).toContain('"type":"heading"')
+    expect(json).toContain('"type":"bulletList"')
+    expect(json).not.toContain('# Title')
+  })
+
+  it('preserves the structural blocks of a multi-block document, in order, on paste', () => {
+    editor = mount()
+    expect(paste(editor, '# Title\n\nA paragraph.\n\n- a\n- b\n\n> quote')).toBe(true)
+    const structural = (editor.getJSON().content ?? [])
+      .map((node) => node.type)
+      .filter((type) => type !== 'paragraph')
+    expect(structural).toEqual(['heading', 'bulletList', 'blockquote'])
+  })
 })

apps/sim/app/workspace/[workspaceId]/files/components/file-viewer/rich-markdown-editor/rich-markdown-editor.css

@@ -380,6 +380,15 @@
   pointer-events: none;
 }
 
+/*
+ * prosemirror-tables' column-resizing plugin toggles the `resize-cursor` class on the editor root
+ * while the pointer is over a column boundary; without this rule the handle shows but the cursor
+ * never changes to the resize affordance.
+ */
+.rich-markdown-prose.resize-cursor {
+  cursor: col-resize;
+}
+
 .rich-markdown-prose p.is-editor-empty:first-child::before {
   content: attr(data-placeholder);
   color: var(--text-subtle);