bug: tool-result media 400s whole request for models without attachment capability

Problem

supportsMediaInToolResult in message-v2.ts returns true unconditionally for @ai-sdk/anthropic and @ai-sdk/openai npm packages. For models with attachment: false (no vision — e.g. GLM-5.2 served through an Anthropic-compatible endpoint), image/PDF attachments from tool results stay inside the tool result and are re-sent on every subsequent turn as part of history replay. The provider then rejects the entire request with a 400 (e.g. Model ... does not appear to support image inputs.), killing the response.

User-visible symptom: a session where a tool returned a screenshot works fine until a later turn — then every response dies with Bad Request: Model ... does not appear to support image inputs., even when the user sends only text.

Why this is a regression: with @ai-sdk/openai-compatible, media was extracted to a user message where unsupportedParts() converted it to a graceful text note ("ERROR: Cannot read image ... Inform the user.") and the model replied normally.

Expected behavior

Media from tool results should be extracted to a user message (degraded gracefully by unsupportedParts()) when the model's attachment capability is false — regardless of the SDK npm package.

Environment

• opencode version: 1.18.14+ (reproducible on dev)
• Model: any with attachment: false served via @ai-sdk/anthropic or @ai-sdk/openai