fix(sync): contain recovery and genesis fork hazards

[QuickMythril]

Summary

• disable peer-claim orphaning by default, ignore the legacy opt-in, restrict the replacement flag to explicit test-network development, and preserve the safe legacy value through managed upgrade and rollback
• exit recovery mode when a recent peer returns and apply recent-only selection in the same synchronization attempt
• defer genesis block-2 minting for a recent higher advertised tip while keeping genesis discovery possible before later-chain signer state exists
• complete T2 in the tracked ultra-review plan; C-03 and N-03 are complete, while N-02 is contained pending the T3 evidence-model redesign

Security boundary

The peer tip and its non-null signature field remain unverified claims. A qualifying peer can defer local genesis minting, but cannot make Core accept or orphan a block. Downloaded blocks still undergo sequential validation, post-genesis signer filtering is unchanged, and public profiles cannot enable peer-claim orphaning. This PR does not change block validity, chain weighting, stale-chain catch-up, release state, or deployment state.

Validation

• red-before-fix evidence: watchdog settings/profile tests failed 5 cases; mixed-peer recovery and fresh-higher genesis policy each failed their target regression
• focused T2 suite: 42 tests, 0 failures/errors/skips
• serialized full Maven suite: 3,020 tests, 0 failures/errors, 68 skipped
• git diff --check passed
• three independent Codex reviews passed after correcting managed rollback behavior, genesis synchronization eligibility, provenance wording, and test-state cleanup