Fix TUI crashes from undefined values (#8588, #8579, #8580)

[blueemp]

Summary

Fixes three TUI crash bugs:

#8588 - enabledFormatters undefined

• Problem: TUI crashes with "undefined is not an object (evaluating 'enabledFormatters().length')" when adding MCP server and running /status
• Root cause: sync.data.formatter is undefined during initialization
• Fix: Added null check sync.data.formatter?.filter((f) => f.enabled) ?? []

#8579 - local.agent.current undefined

• Problem: TUI crashes with "undefined is not an object (evaluating 'local.agent.current().name')" during startup
• Root cause: local.agent.current() returns undefined during initialization
• Fix: Created safe memo currentAgent that returns "build" as fallback, used throughout component

#8580 - ECONNRESET error message

• Problem: Users experiencing "socket connection closed unexpectedly" errors get minimal guidance
• Fix: Enhanced error message to include "If this persists, check your network/proxy settings."

Changes

packages/opencode/src/cli/cmd/tui/component/dialog-status.tsx

• Add null check for sync.data.formatter

packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx

• Add currentAgent memo with safe fallback
• Replace all unsafe local.agent.current().name with currentAgent()

packages/opencode/src/cli/cmd/tui/component/dialog-agent.tsx

• Add null check for local.agent.current()?.name

packages/opencode/src/session/message-v2.ts

• Improve ECONNRESET error message with network/proxy guidance

packages/opencode/test/session/retry.test.ts

• Update tests to match new error message format

Testing

• All existing tests pass (11 tests in retry.test.ts)
• Manual verification of null safety patterns