fix: prompt caching, OpenCode Go MiniMax/Qwen support, Opus 4.7 thinking, SDK compat

- Implement Anthropic prompt caching: first system message + last 2 non-system messages get cache_control: ephemeral, mirroring OpenCode's applyCaching strategy. Move system prompt inline into messages array so providerOptions can attach.
- Add opencode-anthropic provider variant routing MiniMax/Qwen models through the /messages endpoint with x-api-key auth, distinct from the Claude OAuth flow's Bearer auth and Claude Code mimicry.
- Split isAnthropic into isClaudeOAuth (billing header, mcp_ tool prefix, thinking config) and usesAnthropicSDK (cache markers) so non-OAuth Anthropic-format gateways get the right treatment.
- Pin @ai-sdk/anthropic to ^1.2.12: v3 returns LanguageModelV3-spec models that ai v4's streamText rejects at runtime ('AI SDK 4 only supports models that implement specification version v1'). Drop unnecessary V1 casts.
- Restore Opus 4.7 extended thinking by rewriting the outgoing /messages body in the Claude OAuth fetch interceptor: inject thinking: { type: 'adaptive' } (v1 SDK can't emit it), strip temperature/top_p/top_k (Anthropic rejects them with thinking enabled). Gated on max_tokens > 4096 so effort=none still works.
- Bump MAX_STEPS from 10 to 50 to align with AI SDK's stepCountIs(20) default and reduce mid-task halts.
- Fix pre-existing typecheck errors in agent-manager.ts (entry/nextEntry narrowing), app.ts (agentModels body field), KeyUsage.svelte (m guards), and a TS2742 in provider.ts via explicit ModelFactory return type.
- buildFallbackSequence now always returns at least one entry so processMessage runs the agent loop even without keyId/modelId (fixes 4 broken agent-manager tests).

0 files changed, 0 insertions, 0 deletions