Step NC02: Protocol and Shared Kernel

[deku2026]

Summary

• Implements Step NC02: Protocol and Shared Kernel
• Keeps scope limited to the active step
• Updates traceability and acceptance evidence required by the step

Verification

• dotnet restore ArcChat.slnx -m:1 - passed
• dotnet build ArcChat.slnx -m:1 --no-restore /p:TreatWarningsAsErrors=true /clp:ErrorsOnly - passed
• dotnet format ArcChat.slnx --verify-no-changes --no-restore - passed
• dotnet test ArcChat.slnx -m:1 --no-restore /p:TreatWarningsAsErrors=true /clp:ErrorsOnly - passed

Traceability

• Rows updated: NC-PROTO-001 through NC-PROTO-005, NC-NET-001 through NC-NET-006, NC-CORE-008
• Matrices updated: docs/coverage/nc02-protocol-shared-kernel.md, docs/coverage/settings-schema.md, docs/inventory/nc00-environment-toolchain.md, docs/third-party-licenses.md; ArchitectureDesign support PR updates normative traceability matrices
• Final-gate impact: FG.02 protocol/net foundation, FG.04 local persistence foundation, FG.08 settings persistence evidence, FG.09 dependency/license evidence

Out Of Scope

• NC02.F1/NC02.F2 SBE code generation remains deferred because NC08.F1 is not approved
• No UI, agent loop, provider implementations, sync implementation, keychain migration, or server/API replacement behavior is added

Open Questions

• None