chore: incorporate relevant agentbox skel files

Add relevant skeleton files from rcarmo/agentbox/skel for this repo:
- .github/workflows/ci.yml (Makefile checks + conditional Go tests)
- .github/instructions/{00-project-detection,docker-image,frontend-bun,go,python}.instructions.md

Instruction files were adapted where needed to match current workflow names
and repository layout (Go module under go/, Docker workflow filename).

Validated with make check and go test ./... .

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/instructions/python.instructions.md

@@ -0,0 +1,12 @@
+# Python project instructions
+
+Applies when: this repo has `pyproject.toml` or `requirements*.txt`.
+
+## Makefile-first workflow
+- Prefer `make check` as the default validation gate.
+- If you add/change tooling, wire it through Make targets (don't ask users to run raw `pytest`/`ruff`).
+
+## Conventions to implement
+- Prefer `ruff` for lint+format.
+- Prefer `python -m pytest` (and `--cov` for coverage) via Make targets.
+- Keep CI calling Make targets, not raw commands.