Add fix-with-agent capability to PR creation errors

[adboio]

TL;DR

Added "Fix with Agent" functionality to PR creation error dialogs, allowing users to send error context to an active agent session for automated resolution.

Problem

When PR creation fails, users have no way to leverage the agent to diagnose and fix the issue. They can only copy the error message and manually investigate.

Changes

error container with ✨ button	inline chip that holds context about the workflow / intended action

• New hook useFixWithAgent: Manages sending structured error prompts to the active agent session, with validation that a connected session exists
• New utility buildCreatePrFlowErrorPrompt: Generates contextual error prompts that explain the PR creation flow, the failed step, rollback behavior, and common error resolutions
• Updated ErrorContainer component: Added optional "Fix with Agent" button (sparkle icon) alongside the existing copy error button
• Updated CreatePrDialog: Integrated the hook and passes error context builder to enable the fix button when a session is available
• UX improvements: After sending the error to the agent, the dialog closes and the agent's logs panel is activated for visibility

How did you test this?

Changes are integrated into the PR creation flow and will be tested through manual PR creation scenarios with active agent sessions.