net: add summary-only node status wire contract

[Patrick W. Healy (phealy)]

Scope

Stacked on #748. Adds shared JSON/protobuf NodeStatusOverview with explicit peer health and observed route counts/mismatch, separate from heavy peer/route/BPF detail arrays. Protobuf envelope gains additive summary field. Existing publication behavior is unchanged.

366 changed LOC, including generated bindings and contract coverage.

Validation

Shared status tests passed after stacking. Pinned protobuf generation, scoped formatting/lint, race tests and binary builds also passed during implementation. Summary defaults will activate only after transport and consumer migrations.

Lightweight status draft stack

Base: #745. Each layer targets the preceding branch and remains draft.

#746 -> #747 -> #748 -> #750 -> #751 -> #752 -> #753 -> #754 -> #755 -> #756 -> #757 -> #758 -> #759 -> #760 -> #761 -> #762 -> #763 -> #764 -> #765 -> #766 -> #767 -> #768 -> #769 -> #770 -> #771 -> #772 -> #773 -> #774 -> #775 -> #776 -> #777 -> #778 -> #779 -> #780 -> #781 -> #782 -> #783 -> #784 -> #785 -> #786 -> #787 -> #788 -> #789 -> #790 -> #791 -> #792 -> #793 -> #794 -> #795 -> #796 -> #797 -> #798 -> #799

[Patrick W. Healy (phealy)]

This PR was part of the mistaken churn from unnecessarily splitting the lightweight-status work. Its foundation changes are preserved and now reviewed in #812 within the approved 12-PR draft stack.

During consolidation, GitHub automatically marked this PR merged when its rewritten head became an ancestor of its previous feature-branch base, before I retargeted the PR. That ordering was my mistake. I did not perform a PR merge, and nothing was merged or pushed into main. GitHub does not allow reopening a merged PR, so only this review slot needed a replacement PR; the final stack still contains twelve PRs. The automatically deleted head branch has been restored.