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/nightly.sh

@@ -152,8 +152,9 @@ images)
         cp "build/boards/$2" "$OUT/$3"
     done
     # boot_image regenerates these (the source SBOM, and what qemu_session.py also puts back);
-    # the nightly does not change the tree
-    git checkout -q -- sbom.spdx sbom.spdx.json capsules/BLOCK_MAP.md v3/include/version.h
+    # the nightly does not change the tree. v3/include/version.h is untracked since 90c5c140 (#145):
+    # naming it here made git refuse the whole checkout, and set -e end the stage.
+    git checkout -q -- sbom.spdx sbom.spdx.json capsules/BLOCK_MAP.md
     (cd "$OUT" && rm -f pc-stick.img.xz raspi5.img.xz MilkV.img.xz &&
         sha256sum StarshipOS.iso pc-stick.img raspi5.img MilkV.img > SHA256SUMS)
     xz -T0 -6 "$OUT/pc-stick.img" "$OUT/raspi5.img" "$OUT/MilkV.img"