fix(acp-agents): allow deleting remote server entries

[xielixing]

Summary

Fixes #2035

Adds the ability to delete remote server entries from the ACP Agents configuration page. Previously, when a remote SSH server was used, an ACP Agent entry was auto-created but could not be removed. If the server was no longer in use, the entry cluttered the UI indefinitely.

Changes

• AcpAgentsConfig.tsx: Added a deleteRemoteConnection handler that calls sshApi.deleteConnection(), removes the connection from savedConnections state, cleans up probe data, and shows success/error notifications. Added a Delete button (red/danger variant) next to the existing Refresh button for each remote server row.
• Locale files (en-US, zh-CN, zh-TW): Added remote.deleteConnection, remote.deleteConfirm, notifications.deleteConnectionSuccess, and notifications.deleteConnectionFailed keys.

Behavior

1. User clicks the Delete button on a remote server row
2. A confirmation dialog asks: "Remove the remote server "{{name}}" from saved SSH connections? Its ACP agent entries will also be removed."
3. On confirm, sshApi.deleteConnection(connectionId) is called
4. The connection is removed from the saved connections list and probe data is cleaned up
5. A success notification is shown (or error notification on failure)

Validation

• TypeScript: tsc --noEmit passes (no errors in modified files)
• Tests: All 7 existing AcpAgentsConfig.test.tsx tests pass
• i18n audit: pnpm run i18n:audit passes with 0 warnings
• Locale key parity verified across en-US, zh-CN, zh-TW