providers: add MiniMax preset

[octo-patch]

What Changed

• Add a MiniMax provider preset and default credential mapping.
• Route the default runtime and Murph runtime to their protocol-specific MiniMax endpoints, with configuration overrides for both supported regions.
• Document MiniMax-M3 and MiniMax-M2.7 context, modalities, thinking, pricing, and endpoint selection.
• Cover provider parsing, metadata credentials, model mappings, runtime environment generation, and regional endpoint overrides.

Why

Phantom did not have a built-in MiniMax registry entry, so users had to assemble equivalent custom configuration manually.

How I Tested

• bun test (2,648 passed, 10 skipped, 1 todo)
• bun run lint
• bun run typecheck
• A local Agent SDK request capture confirmed that an /anthropic base URL produces exactly one /v1/messages suffix.

Checklist

• Tests pass (bun test)
• Lint passes (bun run lint)
• Typecheck passes (bun run typecheck)
• No secrets or .env files included
• No default exports or barrel files added

[octo-patch]

I added MiniMax to the README provider overview and updated the built-in provider count. I reran bun test, bun run lint, bun run typecheck, and an Agent SDK request capture that confirmed /anthropic/v1/messages.

[octo-patch]

Updated the MiniMax pricing table to match the current target values and pushed a new commit. I ran bun test src/config/__tests__/providers.test.ts src/config/__tests__/loader.test.ts src/config/__tests__/loader-metadata.test.ts src/agent/__tests__/thinking-config.test.ts, bun run lint, and bun run typecheck.

[octo-patch]

Updated MiniMax-M2.7 to use the enabled thinking request shape and corrected the provider documentation. I ran the focused provider and thinking test suite (95 tests) and Biome on the changed TypeScript files.