add search, create and update for helpdoc articles

[ready4god2513]

Add help doc article tools to Teamwork Desk toolset

Adds three new MCP tools for managing help doc articles in Teamwork Desk, exposed under the new twdesk-helpdocs sub-toolset.

New tools

Tool	Description
twdesk-search_helpdoc_articles	Search articles by free-text term, status, site, or category
twdesk-create_helpdoc_article	Create a new article in a given help doc site
twdesk-update_helpdoc_article	Update title, content, description, status, or visibility of an existing article
twdesk-get_helpdoc_article	Fetch a single article by ID

Notes

• Search uses the dedicated GET /search/helpdocs.json endpoint added in desksdkgo v1.0.1 (bumped from v1.0.0), which supports full-text search alongside siteId, status, and categoryId filters.
• The twdesk-helpdocs toolset can be enabled independently via the -toolsets flag.
• 7 tests added covering all tools, including minimal (all-null optional fields) variants.