Support creating a session from a non-GitHub issue URL via a connected MCP server

## Problem

The "Create session from..." entry point only understands github.com pull request and issue links. If you paste an issue URL from another tracker (Azure DevOps, Jira, GitLab, a self-hosted GitHub, and so on), nothing useful happens, even when you already have an MCP server connected for that tool.

## Idea

When the pasted URL is not a github.com link, match its host against the MCP servers the user already has enabled. If one of them appears to serve that host, offer a "Create from " action, grouped under that server's name. Selecting it starts a new session whose first instruction is to fetch the item through that MCP server, read its title and description, and begin work.

Matching is fuzzy and string-based: both the host and the server's name and URL are split into lowercased tokens, short tokens are dropped, and a server is considered a match when one of its tokens and one of the host's tokens contain each other, so the URL lines up with the right server without any hardcoded host list.

### Example

Say you paste:

```
https://dev.azure.com/myorg/myproject/_workitems/edit/1602/
```

and you have an MCP server named `azure-devops` enabled. The host `dev.azure.com` becomes the tokens `azure` (the short pieces `dev` and `com` are dropped). The server `azure-devops` becomes `azure` and `devops`. Both sides share `azure`, so the two match and you get a "Create from dev.azure.com" action under the `azure-devops` group. The same shape works for a `jira` server against a `*.atlassian.net` host, or a `gitlab` server against a GitLab host.

This reuses the existing MCP connection and auth. No new credentials, no tracker-specific integrations to maintain.

## Why this is nice

- One paste box handles GitHub and everything an MCP server can reach.
- If the URL matches nothing, the experience is identical to today, so it stays out of the way until it is useful.
- Adding support for a new tracker means connecting its MCP server, not writing new code.

## Open questions

- How to pick when more than one connected server could plausibly serve the host.
- Whether self-hosted GitHub should go through this path or the native GitHub one.

从现有的“Create session from...”入口点开始，跟踪 GitHub issue 和 pull request URL 的识别方式，然后检查已启用的 MCP 服务器如何公开其名称和 URL。定义主机令牌匹配和服务器分组行为，包括多个匹配项以及自托管 GitHub。完成标准是：受支持的非 GitHub URL 提供适当的操作，而不匹配的 URL 保留当前行为。

由索引模型根据 Issue 内容生成。