feat(policies)!: treat zer0ver 0.x minors as breaking

[onedr0p]

Adds policies/zer0ver.json5, wired into default.json (regenerated via mise run gen). SemVer gives 0.x releases no stability guarantee, and Renovate deliberately classifies 0.x → 0.y as minor, so this preset makes those updates visible as what they are:

• Breaking commit prefix: 0.x minors get feat(scope)!:, consistent with how this repo's semanticCommits policy already marks majors.
• Major branch routing: additionalBranchPrefix: "major-" lands 0.x minors on the same major-<groupSlug> branch Renovate uses to split grouped majors (the default branchName template is {{branchPrefix}}{{additionalBranchPrefix}}{{branchTopic}}), so they stop sharing group PRs with safe patches. Ungrouped deps just get a major- branch rename.

Intentionally not included:

• Labels - this repo ships no label policy, and zer0ver shouldn't introduce one.
• An automerge guard - repo packageRules concatenate after presets, so a consumer's automerge-minors rule would override any guard shipped here. The preset documents the matchCurrentVersion: "!/^v?0/" guard consumers should add themselves.

Proven out in home-operations/renovate-config#64; see home-operations/tuppr#482 for the routing in action.

BREAKING CHANGE: consumers of the bare preset get breaking commit prefixes for 0.x minors, and every open 0.x-minor PR is closed and reopened once under a major- branch. Extend policies/zer0ver.json5 individually (or pin a pre-2.0 tag) to opt in/out explicitly.