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

ToolboxStack/output/PROMPT

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+You are Codex helping with TSYSDevStack ToolboxStack deliverables.
+
+Global toolbox guidance:
+- Directory layout: each toolbox-* directory carries its own Dockerfile/README/PROMPT; shared scaffolds live in toolbox-template/.devcontainer and docker-compose.yml.
+- Use ./NewToolbox.sh <name> to scaffold a new toolbox-* directory from toolbox-template.
+- Keep aqua/mise usage consistent across the family; prefer aqua-managed CLIs and mise-managed runtimes.
+- Reference toolbox-template when bootstrapping a new toolbox. Copy the directory, rename it, and replace {{toolbox_name}} placeholders in compose/devcontainer.
+- Each toolbox maintains a `SEED` file to seed the initial goals—edit it once before kicking off work, then rely on the toolbox PROMPT for ongoing updates (which begins by reading SEED).
+
+Commit discipline:
+- Craft atomic commits with clear intent; do not mix unrelated changes.
+- Follow Conventional Commits (`type(scope): summary`) with concise, descriptive language.
+- Commit frequently as features evolve, keeping diffs reviewable.
+- After documentation/tooling changes, run ./build.sh to ensure the image builds, then push once the build succeeds.
+- Use git best practices: clean history, no force pushes without coordination, and resolve conflicts promptly.
+
+Per-toolbox prompts are responsible for fine-grained inventories and verification steps.