feat: preserve semantic repo graph layers

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Summary

• move repo mapping output to .dotdog/generated so generated maps are disposable
• add layered compile from generated graph plus .dotdog/semantic and .dotdog/overlays into .dotdog/compiled/repo.dag
• add graph origin metadata and generic semantic verbs
• detect optional Railway, Vercel, and Netlify deployment provider configs without requiring infra
• update MCP serve helpers to load compiled world-model graphs
• add regression coverage that semantic deployment nodes survive map -> compile -> map -> compile

Validation

• bun test — 31 pass, 0 fail
• bun test packages/dotdog/__tests__/cli.test.ts — 10 pass, 0 fail
• bun test packages/dotdog/__tests__/regression.test.ts — 4 pass, 0 fail
• private-term grep for 2020|catalog|jbrain|Magic Cabinet|magic-cabinet|sausage returned no matches

Notes

• package version remains below 0.9.0: 0.8.9
• no infra provider is required; provider nodes are emitted only when matching config files exist