docs: describe MCP OAuth tool provider flows

[cursor]

Summary

Documented the MCP OAuth behavior introduced by the merged master change set from PR #621.

Triggering code changes documented here:

• Added per-user MCP OAuth state in the MCP tools response (needsOAuth / authURL) so the webapp can show connection state.
• Added plugin-managed MCP OAuth start and disconnect flows for individual users.
• Updated the Agents RHS tool-provider UI to show Connect and Disconnect for OAuth-backed MCP servers.
• Removed server-posted ephemeral OAuth prompts from conversations.
• Added same-origin validation for resource_metadata during MCP OAuth start.

Documentation files updated:

• docs/admin_guide.md — Added guidance for OAuth-backed MCP servers, including the per-user connection model, System Console behavior, current web/desktop-only connection flow, and the resource_metadata origin requirement.
• docs/user_guide.md — Added end-user instructions for the Agents pane Tools menu, MCP provider Connect / Disconnect behavior, saved provider preferences, and the current mobile limitation.

PR context incorporated from #621:

• The docs note that ephemeral OAuth prompts were intentionally removed and users should use the Agents webapp Tools menu instead.
• The docs note that MCP OAuth connections are currently initiated from Mattermost web or desktop, not mobile.

Screenshots:

• N/A. This is a docs-only change and no screenshots were required or captured.

Borderline items for review:

• None.

Ticket Link

N/A

Screenshots

N/A

Release Note

NONE

  

[github-actions]

🤖 LLM Evaluation Results

OpenAI

⚠️ Overall: 18/19 tests passed (94.7%)

Provider	Total	Passed	Failed	Pass Rate
⚠️ OPENAI	19	18	1	94.7%

❌ Failed Evaluations

Show 1 failures

OPENAI

1. TestReactEval/[openai]_react_cat_message

• Score: 0.00
• Rubric: The word/emoji is a cat emoji or a heart/love emoji
• Reason: The output is the text "heart_eyes_cat", not an actual cat emoji (e.g., 😺/🐱) or a heart/love emoji (e.g., ❤️/😍). Therefore it does not meet the rubric requirement.

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Anthropic

⚠️ Overall: 18/19 tests passed (94.7%)

Provider	Total	Passed	Failed	Pass Rate
⚠️ ANTHROPIC	19	18	1	94.7%

❌ Failed Evaluations

Show 1 failures

ANTHROPIC

1. TestReactEval/[anthropic]_react_cat_message

• Score: 0.00
• Rubric: The word/emoji is a cat emoji or a heart/love emoji
• Reason: The output is the text "heart_eyes_cat", which is not itself a cat emoji or a heart/love emoji character.

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This comment was automatically generated by the eval CI pipeline.