feat: expand replay-backed validation beyond routing-first proposals

[WellDunDun]

Why\nReplay-backed validation now exists for routing proposals, but the active execution plan still lists replay expansion beyond the current routing-first path as unfinished.\n\n## Scope\n- identify where replay materially improves body/description validation\n- extend the replay-backed validation approach beyond routing-only proposals\n- preserve honest fallback semantics when replay is not available\n- update workflow/docs for the expanded validation coverage\n\n## Done when\n- replay-backed validation applies to the next highest-value evolution path after routing\n- provenance and audit surfaces remain coherent\n- tests demonstrate the new replay coverage and fallback behavior