fix: preserve image tool results for Claude

[lantzleiweke]

Summary

• preserve multimodal OpenCode tool results when resuming parked Claude SDK tool calls
• convert base64 image attachments to MCP-native image content blocks
• keep text and image blocks together through the bridge resolver

Root cause

collectToolResults() reduced every tool response to extractTextContent(), and the SDK MCP handler rebuilt a text-only result. OpenCode had stored the PNG attachment correctly, but the provider bridge discarded it before Claude received the tool result.

Verification

• bun test/smoke.ts
• bun run build
• regression fixture confirms text plus PNG data URL converts to MCP { type: "image", data, mimeType } content