Add reload button for cloud agent timeout

[Copilot]

When waiting for a cloud agent response times out after 5 minutes, users have no way to retry the connection without re-submitting their entire request.

Changes

copilotCloudSessionsProvider.ts

• Store retry context (PR, polling state) in a Map when waitForNewSession() times out
• Add "Reload" button to chat stream that executes github.copilot.cloud.sessions.retryPolling command
• Add handleRetryPolling() to restart polling loop using stored context
• Detect special retry message pattern __retry_polling_<prNumber>__ in chatParticipantImpl()

chatSessions.ts

• Register github.copilot.cloud.sessions.retryPolling command that submits retry message to chat via workbench.action.chat.submit

Flow

Timeout occurs
  → Store context in retryContextMap[`pr-${prNumber}`]
  → Display "Reload" button

User clicks button
  → Command submits `__retry_polling_<prNumber>__` to chat
  → chatParticipantImpl() detects pattern
  → handleRetryPolling() retrieves context and restarts polling
  → Cleanup context on success

The retry happens within the same chat context, preserving the conversation and streaming the reconnection progress directly.

Original prompt

When we end up at 'Timed out waiting for the cloud agent to respond', push a 'reload' button to the chat that starts up the polling loop again

The user has attached the following file paths as relevant context:

• .github/copilot-instructions.md

Created from VS Code via the GitHub Pull Request extension.

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