P0.1: Repository and module setup

Go module, Makefile with standard targets, golangci-lint v2 config,
CLAUDE.md, and empty CLI/agent binaries. Build, vet, and lint all pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

PROGRESS_V1.md

@@ -2,7 +2,7 @@
 
 ## Phase 0: Project Scaffolding
 
-- [ ] **P0.1** Repository and module setup
+- [x] **P0.1** Repository and module setup
 - [ ] **P0.2** Proto definitions and code generation
 
 ## Phase 1: Core Libraries