fix: isolate AI review secrets from pull request code

[NianJiuZst]

Summary

• run typecheck, tests, and lint in a separate job that has no repository secrets
• keep the AI review job on the trusted base commit and provide the PR only as inert diff data
• remove MINIMAX_API_KEY and Bash access from the secret-bearing review step
• remove two stale unused test symbols so the newly enforced lint check is green

Root cause

The review job checked out the PR head, injected MINIMAX_API_KEY, allowed Bash, and instructed the agent to run the PR's tests. A same-repository branch could therefore execute attacker-controlled test code in the secret-bearing process.

Impact

PR code still receives normal automated checks, but it no longer executes in the job that holds the review provider credential and a pull-request write token. Live MiniMax smoke tests are intentionally removed from this untrusted workflow.

Validation

• bun test — 376 passed
• bun run typecheck
• bun run lint — 0 errors
• workflow YAML parse
• confirmed the workflow contains neither MINIMAX_API_KEY nor Bash in the reviewer tool allowlist
• git diff --check