feat: add MiniMax as first-class LLM provider

[octo-patch]

Summary

Add MiniMax as a first-class LLM provider alongside OpenAI and Anthropic.

MiniMax offers OpenAI-compatible API with powerful models:

• MiniMax-M2.7 — latest model, 204K context window
• MiniMax-M2.7-highspeed — optimized for speed, 204K context window

Changes

• Provider enum: Add "minimax" to LLMConfigSchema and AgentLLMOverrideSchema
• Factory routing: Handle minimax in createLLMClient() — uses OpenAI SDK internally with MiniMax default base URL
• Temperature clamping: MiniMax requires temperature in (0, 1] — auto-clamped in chatCompletion() and chatWithTools()
• CLI: Update config set-global and init with minimax provider option
• Docs: Update README (zh/en/ja) with MiniMax quick setup and .env.example

Quick setup

inkos config set-global \
  --provider minimax \
  --base-url https://api.minimax.io/v1 \
  --api-key <your-minimax-api-key> \
  --model MiniMax-M2.7

Files changed (11 files, ~474 additions)

File	Change
packages/core/src/models/project.ts	Add minimax to provider enums
packages/core/src/llm/provider.ts	Factory routing, temp clamping
packages/core/src/utils/config-loader.ts	API key required for minimax
packages/cli/src/commands/config.ts	Update provider option text
packages/cli/src/commands/init.ts	Add minimax example in generated .env
.env.example	MiniMax configuration example
README.md / README.en.md / README.ja.md	MiniMax quick setup docs
packages/core/src/__tests__/minimax-provider.test.ts	17 unit tests
packages/core/src/__tests__/minimax-integration.test.ts	3 integration tests

Test plan

• 17 unit tests covering schema validation, client creation, temperature clamping, streaming, and tool calling
• 3 integration tests against real MiniMax API (sync, streaming, system messages)
• All existing tests pass (pre-existing timeouts unrelated to this change)
• Manual: inkos config set-global --provider minimax --base-url https://api.minimax.io/v1 --api-key <key> --model MiniMax-M2.7
• Manual: inkos doctor connectivity check with MiniMax