Feat: add JCEF reload action

[QianKuang8]

Description

Discussion in https://github.com/continuedev/continue/issues/8085

Add a reload button and an action

With manual test, it works well in normal case. Not 100% sure whether it would work when UI freezes.

https://github.com/user-attachments/assets/93b2832a-0b23-4b2c-ac43-9477a9e3eb26

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Checklist

• [] I've read the contributing guide
• [] The relevant docs, if any, have been updated or created
• [] The relevant tests, if any, have been updated or created

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Tests

[ What tests were added or updated to ensure the changes work as expected? ]

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Summary by cubic

Adds a Reload button for the Continue tool window that rebuilds the JCEF browser and client to recover from freezes or crashes.

• New Features

  • Added ReloadBrowserAction and toolbar button to dispose the current JCEF browser and re-create it, then refresh tool window content.
  • ContinueBrowserService now provides reload() and load() to manage lifecycle and re-initialization.

• Bug Fixes

  • Use a dedicated JBCefClient with JS_QUERY_POOL_SIZE=200 set correctly and disposed on teardown.

^{Written for commit 53f5aad7bd0b73ceb1273b7c7ba597c6af73590f. Summary will update automatically on new commits.}