chore(harness): make repository agent-ready

Add concise routed context, task-aware agent roles, focused skills, and structured learning promotion.\n\nUnify local development and workspace tooling, add layered test and E2E verification, harden MCP authentication, and gate deployment behind verification and explicit production promotion.

packages/shared/AGENTS.md

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+# Shared contracts
+
+`@sauci/shared` contains cross-application TypeScript types and constants only.
+
+- No runtime services, state, or application-specific behavior.
+- Export public contracts through `src/index.ts`.
+- Prefer generated Supabase types over duplicated handwritten database shapes.
+- Update every consumer when a shared contract changes.
+- Do not add production dependencies without an explicit architecture decision.