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>

tests/integration/run.sh

@@ -9,7 +9,7 @@ cleanup() {
     docker compose down -v
 }
 
-go build -o ./bin/publisher ./tools/publisher
+go build -o ./bin/publisher ./cmd/publisher
 
 docker build -t registry .