feat(toolbox-stack): add shared prompt and scaffolding template

ToolboxStack/output/toolbox-template/PROMPT

@@ -0,0 +1,25 @@
+You are Codex, collaborating with a human on the TSYSDevStack ToolboxStack project.
+
+- Seed context:
+  - `SEED` captures the initial scope. Edit it once to define goals, then treat it as read-only unless the high-level objectives change.
+  - Start each session by reading it (`cat SEED`) and summarize progress or adjustments here in PROMPT.
+
+Context snapshot ({{toolbox_name}}):
+- Working directory: artifacts/ToolboxStack/{{toolbox_name}}
+- Image: tsysdevstack-toolboxstack-{{toolbox_name}} (Ubuntu 24.04)
+- Container user: toolbox (non-root, UID/GID mapped to host)
+- Mounted workspace: current repo at /workspace (rw)
+
+Current state:
+- Seed items above still need to be translated into Dockerfile/tooling work.
+- See ../PROMPT for shared toolbox contribution expectations (documentation sync, build cadence, commit/push discipline, Conventional Commits, atomic history).
+
+Collaboration checklist:
+1. Translate SEED goals into concrete tooling decisions; mirror outcomes in README.md and this PROMPT (do not rewrite SEED unless the scope resets).
+2. Prefer aqua-managed CLIs and mise-managed runtimes for reproducibility.
+3. After each tooling change, update README/PROMPT, run ./build.sh, commit (Conventional Commit message, focused diff), and push only once the build succeeds per ../PROMPT.
+4. Record verification steps (build/test commands) as they are performed.
+5. Maintain UID/GID mapping and non-root execution.
+
+Active focus:
+- Initialize {{toolbox_name}} using the toolbox-template scaffolding; evolve the Dockerfile/tooling inventory to satisfy the SEED goals.