fix: put-backs no longer name the untracked version.h (#145)

90c5c140 untracked v3/include/version.h, but six places still put it back
with git checkout. Git refuses the whole checkout when one path is unknown:

- scripts/nightly.sh images (set -e): the stage ended there, so the nightly
  (images, publish, proofs) and release.yml (images, docs, gitea-release)
  would fail. Acceptance does not run images, so it passed.
- scripts/check_images.sh (no -e), demo/build-iso.sh, demo/mint-zuse.sh
  (|| true): silently put nothing back, BLOCK_MAP.md and the SBOM included.
- scripts/qemu_session.py: an error after every boot, otherwise harmless.
- boards/BRINGUP.md: the step said to put it back.

BLOCK_MAP.md stays in every put-back: a signed build (CI's) still rewrites
its Signed column. Found while setting up alpha.5; Captain Bob: fix it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017RzZgrf7V7Zk2iczBXDRbm

scripts/check_images.sh

@@ -178,7 +178,7 @@ check "a good format reads back" "$MKARTEMIS" --format "$T/t.img" --first-lba 20
 rm -f "$T/t.img"
 
 # the builds regenerate these; put them back as committed (as qemu_session.py does)
-git checkout -q -- v3/include/version.h capsules/BLOCK_MAP.md sbom.spdx sbom.spdx.json
+git checkout -q -- capsules/BLOCK_MAP.md sbom.spdx sbom.spdx.json      # version.h is untracked (#145)
 
 echo "RESULT: $([ $ok = 1 ] && echo PASS || echo FAIL)"
 [ $ok = 1 ]