fix(web): disable indented code blocks in markdown rendering (#395)

* fix(web): disable indented code blocks in markdown rendering

In CommonMark, text indented by 4+ spaces is treated as a code block.
LLM responses frequently have indented content inside numbered lists or
quoted text, causing large chunks to render as a single code block
instead of formatted markdown.

Add a remark plugin that disables the codeIndented tokenizer. Fenced
code blocks (``` … ```) continue to work normally.

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Co-Authored-By: HAPI <noreply@hapi.run>

* fix(web): fix typecheck for remark plugin this binding

Use `as any` cast for the unified processor `this` context instead of
an explicit type annotation that conflicts with the Processor type.

via [HAPI](https://hapi.run)

Co-Authored-By: HAPI <noreply@hapi.run>

* fix(web): use this:unknown annotation to satisfy noImplicitThis

The previous `as any` cast on `this` still triggers noImplicitThis in
strict mode. Annotate the parameter as `this: unknown` and cast to
the required shape inside the function body. Also use the key-based
`data(key, value)` API instead of mutating the returned object.

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Co-Authored-By: HAPI <noreply@hapi.run>

---------

Co-authored-by: HAPI <noreply@hapi.run>

web/src/components/assistant-ui/markdown-text.tsx

@@ -6,12 +6,13 @@ import {
     type CodeHeaderProps,
 } from '@assistant-ui/react-markdown'
 import remarkGfm from 'remark-gfm'
+import remarkDisableIndentedCode from '@/lib/remark-disable-indented-code'
 import { cn } from '@/lib/utils'
 import { SyntaxHighlighter } from '@/components/assistant-ui/shiki-highlighter'
 import { useCopyToClipboard } from '@/hooks/useCopyToClipboard'
 import { CopyIcon, CheckIcon } from '@/components/icons'
 
-export const MARKDOWN_PLUGINS = [remarkGfm]
+export const MARKDOWN_PLUGINS = [remarkGfm, remarkDisableIndentedCode]
 
 function CodeHeader(props: CodeHeaderProps) {
     const { copied, copy } = useCopyToClipboard()

web/src/lib/remark-disable-indented-code.ts

@@ -0,0 +1,14 @@
+/**
+ * Remark plugin that disables indented code blocks (4-space indent).
+ *
+ * In CommonMark, text indented by 4+ spaces becomes a code block.  This
+ * frequently misparses LLM output where numbered-list items with nested
+ * content or quoted text are indented.  Fenced code blocks (``` … ```)
+ * still work normally.
+ */
+export default function remarkDisableIndentedCode(this: unknown) {
+    const processor = this as { data(key: string, value?: unknown): unknown }
+    const micromarkExtensions = (processor.data('micromarkExtensions') ?? []) as unknown[]
+    micromarkExtensions.push({ disable: { null: ['codeIndented'] } })
+    processor.data('micromarkExtensions', micromarkExtensions)
+}