ci: add OpenCodeReview PR review workflow

[erubboli]

What

Adds an AI code review workflow via OpenCodeReview v1.12.0 on GitHub-hosted runners. On every PR (opened / synchronized / reopened) it reviews the merge-base..head diff and posts inline review comments plus a sticky summary.

Config

Setting	Value
Model	glm-5.3-flash via z.ai Coding Plan (https://api.z.ai/api/coding/paas/v4)
Reasoning	thinking: enabled + reasoning_effort: low (fast/cheap; GLM-5.3 rejects disabled — the action's default — hence the explicit override)
Budget	500k tokens/review — exceeding it stops dispatch and publishes partial results (exit 0, not a failure)
Noise control	incremental: true (no dup comments on re-push), severity low routed to summary instead of inline
Fork PRs	skipped (head.repo.fork == false) — forks can't read secrets anyway
Concurrency	one run per PR, superseded pushes cancel in-flight runs

Notes

• Requires repo secret OCR_LLM_TOKEN (set).
• Advisory only — never blocks merges.
• If the key turns out to be a standard API key rather than Coding Plan, flip llm_url to https://api.z.ai/api/paas/v4.
• Rollback = revert this PR (single file).

Test plan

• Merge, open/refresh a PR, confirm the "AI Code Review" run posts inline comments + summary
• If 401/404 from LLM: switch endpoint to https://api.z.ai/api/paas/v4

[github-actions]

✅ OpenCodeReview: Review complete: 0 finding(s) across 1 selected item(s).