Rename generate target to proto; dev data dir run/ -> srv/

Aligns with the platform engineering standards.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

PROJECT_PLAN.md

@@ -472,7 +472,7 @@ See ARCHITECTURE.md §18 for full design rationale and artifact inventory.
   - `build` — compile all binaries to `bin/`
   - `test` — `go test -race ./...`
   - `lint` — `golangci-lint run ./...`
-  - `generate` — `go generate ./...` (proto stubs from Phase 7)
+  - `proto` — `go generate ./...` (proto stubs from Phase 7)
   - `man` — build compressed man pages
   - `install` — run `dist/install.sh`
   - `docker` — `docker build -t mcias:$(VERSION) -t mcias:latest .`