Consolidate markdown rendering — Manager has custom regex parser instead of shared `marked`

## Recommendation

### 🔀 CONSOLIDATE: Use Shared Markdown Library

The Manager module has its own custom regex-based markdown parser instead of using the shared `marked` library used elsewhere in the codebase.

## What Was Found

- **Shared**: `marked` library used by most of the codebase
- **Custom**: Manager has a regex-based markdown parser
- Custom parser is less robust and harder to maintain

## How to Fix

1. Replace Manager's custom markdown parser with the shared `marked` utility
2. Verify rendered output matches expectations
3. Remove custom parser

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**Category:** Conflicting Systems | **Priority:** Recommended | **Effort:** Small
Part of #11022
_Filed by repo-audit skill_

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-11068-Consolidate-markdown-rendering-Manager-has-custom-regex-parser-instead-of-shared-m-33e6d73d3650810bb2ebe34bc2d9b262) by [Unito](https://www.unito.io)

Locate the Manager module and its custom regex-based markdown parser, then compare it with the shared marked utility used elsewhere in the codebase. Replace the custom parser, verify that rendered output matches expectations, and remove the old parser.

Written by the indexing model from the issue text.