R: Manually runnable hyperlinks can be pasted in the wrong console when multiple are active

Follow up to https://github.com/posit-dev/positron/pull/7313

With the following reprex:

• Start R console 1
• Start R console 2
• Run cli::cli_alert("{.run revdepcheck::cloud_summary()}") in R console 2 and click the hyperlink.
• The pasted code will incorrectly end up in R console 1.

https://github.com/user-attachments/assets/74cc62b3-d3ef-4f3b-89e0-ce1a284c66e4

This is due to our call to positron.window.getConsoleForLanguage() here:
https://github.com/posit-dev/positron/blob/6af5bd88e7ff43e833efd238a6a9bc077800059a/extensions/positron-r/src/hyperlink.ts#L51

It chooses the wrong console due to how $getSessionIdForLanguage() works, which just chooses the first session id that matches the language id.

$getSessionIdForLanguage() was introduced in https://github.com/posit-dev/positron/pull/7313, but that was to restore the original pre-multi-session-world behavior, since adding multi-session support accidentally broke the feature entirely.

This issue is about further enhancing $getSessionIdForLanguage() to correctly support multi-session, which means that $getSessionIdForLanguage() will need to switch from:

"choose the first session id that matches the language id"

to:

"choose the most recently active (and still alive) session id that matches the language id"

We may need some additional helper to query the most recently active session id for a language, I'm not sure yet.

Start in extensions/positron-r/src/hyperlink.ts at the call to positron.window.getConsoleForLanguage(), then trace $getSessionIdForLanguage() and its session-selection logic. Reproduce the two-console R scenario from the issue; done means a manually runnable hyperlink from the most recently active live R session pastes into that session rather than the first one.