chore: add local DCO check via pre-commit commit-msg hook

[ajbozarth]

Issue

Fixes #

Description

Adds a commit-msg-stage pre-commit hook that fails commits missing a Signed-off-by trailer, complementing the GitHub DCO bot enabled in #1129. Surfaces the same DCO check locally so contributors find out at commit time instead of after pushing.

default_install_hook_types: [pre-commit, commit-msg] ensures pre-commit install wires up both hook types automatically — no special install flags needed.

Existing contributors: re-run pre-commit install once after pulling this branch to pick up the new commit-msg hook.

Long-time contributors: if your .git/hooks/ directory has leftover pre-commit.legacy or pre-commit.old files from previous migrations, pre-commit install will detect them, enter migration mode, and silently skip installing the new commit-msg hook. After running pre-commit install, check for .git/hooks/commit-msg — if it's missing, run the explicit form once:

pre-commit install --hook-type commit-msg

After that, future config changes are picked up automatically with no further action.

Testing

• Tests added to the respective file if code was changed
• New code has 100% coverage if code was added
• Ensure existing tests and github automation passes (a maintainer will kick off the github automation when the rest of the PR is populated)

Manually verified on clean clones:

• Fresh clone + pre-commit install installs both pre-commit and commit-msg hooks
• Existing-contributor path (clone, install pre-commit on main, switch to this branch, re-run pre-commit install) also installs both hooks
• git commit -m "..." (no -s) fails with Missing Signed-off-by trailer. Use: git commit -s
• git commit -s -m "..." passes the DCO check

Attribution

• AI coding assistants used

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Adding a new component, requirement, sampling strategy, or tool?

• Component
• Requirement
• Sampling Strategy
• Tool