The codegen tests write into the working tree

Still open, and now the only writer left. #4135 stopped the drift check writing into the tree; the suite itself still renders in place, so a run of compass check can leave generated files changed that the branch never touched.

Make the codegen suite render into a temporary directory, or restore what it touches, so that running a check never leaves the working tree different from how it was found.

A run of `compass check` on a branch left two generated files modified that the branch had not touched: `ores.refdata.api/domain/calendar_rule.hpp` and `ores.reporting/core/tests/report_error_eventing_integration_tests.cpp`. The first lost a paragraph of documentation that the model does not carry, so committing it would have silently reverted a colleague's work. The second gained two lines that no gate asks for.

Both were side effects of running the suite rather than the branch's change, and `drift-sweep` passes with both reverted, which is how they were identified. That takes a deliberate experiment to establish. A person who runs the checks, sees a dirty tree, and commits what looks like their own work will merge someone else's file back to an older shape.

The reason the experiment was needed is that the check that would catch drift compares the working tree against HEAD, so it reports an uncommitted fix and an uncommitted side effect identically.

• `drift-sweep`, which renders every catalogue component and passed with both files reverted.
• The generated-file drift captures, which describe the same confusion between a hand edit and a render.

• The drift check is destructive on a stale template branch.
• Main lost the batch members a consumer uses. Capture — what an inbox capture is.