AutoStory M1 Shared AutoStory and navigation core #135

• Scope: shared select database, story index and stats (SV refactors), grid and route planner, ScreenMachine/StepTrace, JSON maps and loader, LegWalker and the route log, story events and segments, story steps and run options (checkpoint dropdowns, Checks, language, attempts).
• PRs: U1–U10, from fork #43, #44, #45, #114, #122. About 5k code, 3.3k tests.
• Done when: all merged upstream, with unit tests green on three platforms. No game behaviour changes except SV's dropdowns, which keep the same labels.
• Follow-ups: a joined multi-map view and coord events in the map schema (requested by BDSP).

Tracked by the AutoStory master issue. Design: AutoStory-Architecture.md; PR tree and sizes: FRLG_SIZING.md.