[davidmoralesz]

What & why

Aligns the dev tooling with studiobimo/project-template, so the shared parts stop being hand-copied.

• Shared Makefile targets move to .devtools/base.mk; the Makefile keeps validate, build, check, lock and clean.
• The branch, PR-size and commit-message checks now come from the studiobimo/.github hook repo at v1.5.0. The local script copies are deleted, and agent-guard.sh runs the hooks by id.
• Files and marked blocks the template manages are synced; template-sync.sh and a weekly template-drift.yml keep them that way.

No pack content changes.

Two things this depends on before CI can pass:

• Lint clones studiobimo/.github as a pre-commit hook repo, which only works from CI once that repo is public.
• template-drift.yml calls ci-template-drift.yml@v1, which arrives with feat(workflows): add a template drift check .github#38, and needs the template to have a release.

Checklist

• PR title is a Conventional Commit (it becomes the squash commit)
• ≤20 files changed (otherwise split with gh stack)
• make -C .devtools check passes locally
• Tested in game on the Minecraft version in pack.toml: not applicable, tooling only; the built zip is unchanged in content
• Only the pack's own namespace and minecraft are used; nothing copied from third-party packs
• The pack's README is updated if behavior changed: not applicable