Rea CI Tests Audit

# REA CI and tests audit

Establish which checks still catch real regressions and which costs can be
removed without losing that protection. The outcome may be a verified fix,
an evidence-backed recommendation, or an explicit decision to stop.

Follow the checkout's `AGENTS.md`, [testing guide](../../../docs/testing.md),
and [contribution rules](../../../CONTRIBUTING.md). Use their current commands
and pinned toolchain, rather than commands remembered from an earlier audit.
Preserve the requested scope: investigation alone does not authorize edits;
this skill does not grant permission to publish issues, push, or merge. Existing
user authorization still applies. Keep audit notes and raw results outside the
tracked tree, normally in a task-specific `/tmp` directory.

## Establish the executed baseline

Fetch when the user asks for latest main. Pin the baseline SHA and inspected
workflow revision; use an isolated worktree when changing or comparing code.
Do not modify another task's checkout. Record dirty changes and the exact
command, toolchain, host, selected tests, instrumentation, and prerequisites.
An old run is evidence for its executed revision, even if main advances.

Trace workflow triggers, changed-path selection, job dependencies, reusable
actions, package scripts, test discovery, artifact producers, and report gates
through to the commands that actually execute. Include scripts, generated data,