cmux-runner-hook: classify cmux-next frame-pacing's build and bench

[teamleaderleo]

cmux's nightly cmux-next-frame-pacing.yml (manaflow-ai/cmux#16511, merged as f204ade4df3) runs two jobs on the side lane. The hook didn't recognize either of them under that workflow, so both fell back to the compile class. That class takes the persistent-dd token and a canonical root, and neither job uses them.

• build calls reload-build.yml through workflow_call. Inside a called workflow, GITHUB_WORKFLOW_REF names the caller, so the hook sees (cmux-next-frame-pacing.yml, build). The work is reload-build's Debug build into the workspace, so it is isolated, matching (reload-build.yml, build).
• bench unpacks the app into $RUNNER_TEMP and drives the console session. Before those steps it takes the gui token itself with glaeda-canonical-root take-gui --wait 900, the same way test-e2e's test does, so it is gui-step. It restores no product into a canonical root. On a one-root mini, gui-step takes gui and the root when the job starts, take-gui is then a no-op, and the workflow accepts exit 0 or 2.

Commits: a71b1d3 adds the failing test, ff9608f adds the classes.

Red (a71b1d3): python3 scripts/test-glaeda-cmux-runner.py HookTest.test_job_class_keys_on_workflow_file_and_job_id failed with ('compile', True) != ('isolated', False).
Green (ff9608f): the same command passes. -k gui_step and NoEmDashTest also pass.

Rollout: job-started.sh runs the staged hook fresh for each job, but the minis only pick up this change after a glaeda-cmux-runner-fleet --apply (or OTA). That rollout is not part of this PR.

🤖 Generated with Claude Code

https://claude.ai/code/session_01RYQHfug1ZVQDp4eWgwVUtD

[teamleaderleo]

Subagent review at ff9608f: APPROVE. build resolves to (cmux-next-frame-pacing.yml, build) via the caller's GITHUB_WORKFLOW_REF, like cmux-tui's build; gui-step admission plus the workflow's take-gui 0|2 handling never runs the bench without the gui token, and has no root/gui lock-order deadlock. Non-blocking: on a one-root mini the bench holds the root it doesn't use (nightly, quiet hour); a locked console refuses the job at job-started (red, not skipped).