Add GLM-5.2 harness support

[byapparov]

Summary

Add GLM-5.2 support for the Z.AI Coding Plan harness, including fallback model metadata, effort mapping, and request payload coverage.

Issues addressed

• Adds zai-coding-plan/glm-5.2 metadata for stale local model snapshots.
• Maps GLM-5.2 variants to supported Z.AI efforts: low|medium|high -> high, xhigh|max -> max.
• Verifies Coding Plan stream payload sends preserved thinking and reasoning_effort: max.

Verified false

• None.

Not addressed

• Does not regenerate the ignored local models-snapshot.ts; runtime fallback handles stale snapshots and the live models.dev entry is already present.

Test plan

• bun test test/provider/transform.test.ts --timeout 30000
• bun test test/session/llm.test.ts --timeout 30000
• bun test test/provider/provider.test.ts --timeout 30000
• bun run typecheck
• git diff --check
• pre-push bun turbo typecheck

[aictrl-dev]

I have enough to finalize the review. Let me confirm the overwriting loop context once more, then record.