Stability Pass + Stats Overhaul — System.Execute Steam update #1405010

Quality-of-life and stability update. New Statistics view, expanded save system, and a round of fixes from a top-to-bottom code review. New Statistics page rebuilt: 5 grouped sections, lifetime aggregates across all slots, leaderboard ranks, and per-save breakdown Save slots expanded from 5 to 20, with sorting, usage counter, and a reworked saves UI Credits view: widened layout, 3-column technology grid, EQ visualizer, version footer Gameplay manual expanded with new lore fragments and updated hints Terminal timestamps toggle added to Settings Settings: confirmation on reset, clearer hints Stability & Hardening Renderer errors are now forwarded to the main log file so crashes can actually be diagnosed Save migration refuses to load saves from a newer version than this build, instead of silently downgrading them Removed an unverified save-file "checksum" that was decorative, not protectiv...