fix(examples): give gn-bundle-roundtrip a falsifier that can fail

[TMHSDigital]

Closes #349.

Problem

The gn-bundle-roundtrip catalog falsifier expected exit 2 for --legacy-rna, but exit 2 meant four different things:

• 5.x rejects the legacy node, which is the expected outcome;
• the legacy node unexpectedly exists, meaning the contract broke;
• the carrier mesh was rewritten;
• argparse rejected an unknown flag.

So the row passed whether or not the contract held, and would have passed even if the flag were deleted.

Change

• gn_bundle_roundtrip.py: the carrier-rewritten check moves to 6, the expected legacy-node rejection to 7, and an unexpectedly accepted legacy node to 8.
• tests/smoke/catalog.json: expects 7.
• tests/check_smoke_catalog.py: FORBIDDEN_EXITS now includes 2 (argparse usage). CLAUDE.md § Smoke and the checker docstring are updated to match.
• README: the exit table, the failure list and the measured matrix are updated. The smoke line now states the catalog falsifier (this example's instance of examples: 60 of 64 READMEs say smoke 'does not pass' the flag CI actually runs as the falsifier #359).

Evidence

Proven by live run (--factory-startup --python-exit-code 1; binary reports 5.2.1 LTS):

Args	Exit	stderr
(none)	0
--legacy-rna	7	ERROR: RuntimeError: Error: Node type GeometryNodeCombineBundle undefined
--legacy-rnaX (simulated deleted flag)	2	error: unrecognized arguments: --legacy-rnaX

The old row (expect_exit: 2) would have accepted that last line.

Lint falsified: with the catalog row set back to expect_exit: 2, python tests/check_smoke_catalog.py prints ::error::catalog row 'gn-bundle-roundtrip' falsifier 0: expect_exit 2 must be an int other than 0, 1, 2, 77 and exits 1. Restored, it passes.

Not run locally:

• The README's 5.0.1 and 5.1.2 columns were updated by inspection. The renumbered branch does not depend on the version.
• 4.5 skips with exit 77, unchanged.
• check_exit_code_readme.py, check_falsifier_targets.py and check_smoke_catalog.py pass.

🤖 Generated with Claude Code

[TMHSDigital]

CI evidence before merge: all checks pass ( 13 pass ). Blender Smoke on PR head: Blender 5.2.2 LTS / Blender 4.5.14 LTS. Summaries (happy path; falsifiers) per leg: 143 passed, 1 skipped, 0 failed;142 passed, 0 skipped, 0 failed;141 passed, 3 skipped, 0 failed;136 passed, 6 skipped, 0 failed;