feat(architecture): phase 3 local run use-case extraction

[Lythaeon]

Summary

• extract local run orchestration into application::local_run::execute(command, ports)
• introduce explicit local-run ports for shutdown, traffic, metrics, and outputs
• reduce src/app/runner/core/mod.rs to adapter composition for concrete runtime modules
• add unit tests for the extracted use-case flow and splash-cancel behavior
• update architecture migration plan with implemented Phase 2 and Phase 3 artifacts

Rationale And Tradeoffs

• keeps behavior stable while introducing a migration seam for further hexagonal extraction
• ports are currently coarse-grained to minimize risk; Phase 4+ can refine boundaries further

Validation

• cargo make format
• cargo make clippy
• cargo make test
• cargo make test-wasm