[Stage 0.4] Prepare and verify rulesets for main and v2

[draedful]

Parent: #310

Goal

Protect the stable v1 line and ensure the v2 line is protected from the moment its branch is created.

Scope

• Assign a repository or organization admin owner for this task.
• Configure the main ruleset.
• Configure a ruleset targeting the future v2 branch name before the Git ref is created.
• Require changes to go through pull requests.
• Require the agreed CI, test, E2E, and package-contract checks.
• Require at least one approval and resolved review conversations.
• Prevent branch deletion and force pushes.
• Allow merge commits for manual main to v2 synchronization.
• Do not require linear history on v2 if that would reject synchronization merge commits.
• Preserve release automation through only the minimum required bypass.
• Verify the effective v2 rules immediately after branch creation.

The future release/v1 ruleset is also prepared before the cutover creates that branch.

Acceptance criteria

• An admin owner is assigned.
• main is covered by an active ruleset.
• A ruleset targeting v2 exists before branch creation.
• Direct unreviewed changes, force pushes, and branch deletion are rejected.
• Required checks must pass before merge.
• Merge-commit synchronization into v2 is permitted.
• Release automation has only the minimum bypass permission it needs.
• The ruleset becomes effective and is verified when v2 is created.
• The future release/v1 protection procedure and owner are documented.