Add GLM 5.3 to live bench

[anthonypizzolato-abacus]

Add GLM 5.3 to live bench

• Model: GLM-5.3 (Z.ai / Zhipu AI), released 2026-08-14 — flagship coding/agentic model, open-weights SOTA on Terminal-Bench 3.0 and Agents' Last Exam (CLI). Docs: https://docs.z.ai/guides/llm/glm-5.3
• Provider API ID: glm-5.3 on the first-party Z.ai API (https://api.z.ai/api/paas/v4, OpenAI-compatible)
• Context window: 1M tokens (1,048,576); max output 128K
• Note: the standalone GLM-5.3 API is rolling out ("coming soon" per the docs page; currently available via the GLM Coding Plan) — runs will work as soon as the endpoint opens.

Changes

• lcb_runner/lm_styles.py — new LMStyle.ZAIAPI member; LanguageModel("glm-5.3", "GLM-5.3", LMStyle.ZAIAPI, datetime(2026, 8, 14), link=...) added after the DeepSeek first-party API entries
• lcb_runner/runner/zai_runner.py — new ZAIRunner (env key ZAI_API_KEY), mirroring DeepSeekRunner exactly
• lcb_runner/runner/runner_utils.py — build_runner branch for LMStyle.ZAIAPI
• lcb_runner/prompts/code_generation.py — ZAIAPI added to the generic-chat-prompt style list

[anthonypizzolato-abacus]

🔄 Re-verified 2026-08-18: this PR is still open and merges cleanly into current main (no conflicts).

Availability update since the PR was opened: the GLM-5.3 API is now live — z.ai serves it to GLM Coding Plan users via https://api.z.ai/api/paas/v4 (the endpoint this PR's ZAIRunner targets), and OpenRouter also lists z-ai/glm-5.3 at the same official rates ($1.40/$4.40 per 1M, cached $0.26 — cross-checked against docs.z.ai/guides/overview/pricing). Bench runs should now work with a ZAI_API_KEY from a Coding-Plan account.