bump-consumers: regenerate the umbrella's wiring block in its bump commit #78

What

Since MIP-0076 row 15 (marola-dev/marola#750), the umbrella's quality-other runs wiring --check, and REPOS.md's generated block lists every repo's devkit pins (the "a marola-devkit tag" row). bump-consumers moves the umbrella's own pins without regenerating that block, so every umbrella bump PR fails the gate as stale: marola-dev/marola#764 (v0.8.2) did, and was fixed by hand with one regenerated line. Left as is, it also blocks marola-dev/marola#762's auto-merge outright: the umbrella is the canary, so its bump would never go green and no code repo would follow.

Fix: when bump-consumers bumps a repo that has docs/2-Building-marola/REPOS.md with the wiring markers (today only the umbrella), it checks out that repo's submodules and runs the new tag's wiring docs/2-Building-marola/REPOS.md before committing, so the bump commit carries the regenerated block, the same way pointer-sync.sh does for pointer moves (marola-dev/marola#738). It must use the wiring at the tag it is bumping to (the release just published), not the job's own checkout.

Acceptance criteria

• an umbrella bump PR's commit includes the regenerated REPOS.md block, and its quality-other is green with no hand edit
• repos without the markers are bumped exactly as today

Named test

bump-consumers --self-test with umbrella_bump_regenerates_wiring_block (a fake wiring on PATH: the bump commit carries its edit) and repo_without_markers_unchanged; the next release's umbrella bump PR green (link).