#30333 ci(web): run session info check in warn branch

HOLD: duplicate of #30261; do not land.

The feat-cmux-next checks job was red because the webviews warn branch skipped the newly added check:session-info-names package check. This left the aggregate structure test red even though the check could not run on the warn path.

This wires check:session-info-names into the existing warn-only loop. It keeps the same bun run ... || warning behavior as the other style checks, while preserving the fail path for non-feat branches.

Leo's standing rule is that display tests gate nothing; this repair is CI structure only and does not change display coverage.

Prior art: #29921 introduced check:session-info-names; #24438 established the check:pieces and warn-branch split; #29666 and #28511 preserve the existing webview gate structure.

Validation:

• tests.test_cmux_next_checks_workflow.WebviewsWarnSplitCoversCheck.test_every_part_of_bun_run_check_runs_in_the_warn_branch passes locally.
• Fleet focused check will run on this PR.

Risk: CI workflow only; no product behavior or permissions change.

Agent session: agent session

🤖 Generated with Claude Code

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Summary by cubic

Fixes the feat-cmux-next checks job by running the check:session-info-names check in the webviews warn branch, so the aggregate structure test no longer stays red when the check can't run on that path.

The check joins the existing warn-only loop with the same bun run ... || warning behavior as the other style checks, while preserving the fail path for non-feat branches. Display tests still gate nothing; this is CI structure only.