Move publisher CLI from tools/ to cmd/ (#326)

## Summary

Move the publisher CLI from `tools/publisher/` to `cmd/publisher/` as
it's a proper application rather than a development utility.

This addresses feedback from @rdimitrov in PR #324 that the publisher
CLI should be under `cmd/` since it's not really a tool in the same
sense as other helpers in the `tools/` folder.

## Changes

- Moved `tools/publisher/` directory to `cmd/publisher/`
- Updated Makefile build and clean targets
- Updated README.md documentation links
- Updated VS Code launch configuration
- Updated integration test script
- Updated FAQ documentation
- Fixed Go import paths in publisher code

---------

Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>
Co-authored-by: adam jones <domdomegg@users.noreply.github.com>

Makefile

@@ -10,7 +10,7 @@ build: ## Build the registry application
 	go build -o bin/registry ./cmd/registry
 
 publisher: ## Build the publisher tool
-	cd tools/publisher && ./build.sh
+	cd cmd/publisher && ./build.sh
 
 # Test targets
 test-unit: ## Run unit tests with coverage
@@ -64,7 +64,7 @@ dev-local: ## Run registry locally
 clean: ## Clean build artifacts and coverage files
 	rm -rf bin
 	rm -f coverage.out coverage.html
-	cd tools/publisher && rm -f publisher
+	cd cmd/publisher && rm -f publisher
 
 
 .DEFAULT_GOAL := help