Add Kimi Code provider

[auroter]

Summary

• add a kimi-code setup preset for Kimi Code membership credentials and the https://api.kimi.com/coding/v1 endpoint
• offer only the four model IDs verified through the live endpoint: k3-256k, k3, kimi-for-coding, and kimi-for-coding-highspeed
• use valid high reasoning effort for K3 models and omit unsupported reasoning_effort for the K2.7-backed coding aliases
• explain Kimi Code/Open Platform key isolation after 401 responses and write provider config files with mode 0600
• document the setup flow and add catalog, endpoint, setup, permissions, diagnostics, and reasoning regression coverage

Verification

• live completion returned exactly PONG for all four advertised Kimi Code models
• the exact committed PR snapshot passes 157 focused provider, setup, fallback, budget, and reasoning tests
• scoped Ruff lint and format checks passed on the committed snapshot
• git diff --check passed; no credentials are included in this PR

Scope

Kimi Open Platform is intentionally not included because its credentials are isolated from Kimi Code and no Open Platform key was available for live validation.

Repository baseline notes

• the strict full-suite command currently stops during collection because the existing integration marker is not registered
• the normal full suite reached 2913 passed, 26 skipped; its 18 failures are existing sandbox tests that require a locally available Docker executable
• repo-wide Ruff, scoped mypy, and strict docs checks also have existing failures in untouched files

[auroter]

Live sanity after the K2.7 fix passed: model=kimi-for-coding, resolved reasoning_effort=None, response=PONG. The focused provider regression suite also passes with 165 tests.

[whatever]

lgtm

[auroter]

Scope update: this PR now includes only Kimi Code. Live completion returned PONG for every advertised model: k3-256k, k3, kimi-for-coding, and kimi-for-coding-highspeed. Kimi Open Platform and its unverified model IDs were removed.