Seed CLI layer for platform tools

[codeforester]

Summary

Seed the Base Platform Tools CLI layer so future utilities have a clear home for Bash and Python command implementations.

Rationale

Base Platform Tools should reuse Base as the workstation control plane instead of copying Base internals. The repository needs a small, documented CLI layout that makes this boundary explicit:

• Base owns basectl.
• Base owns base-wrapper.
• Base Platform Tools owns optional tool implementations.
• base_manifest.yaml declares runnable project commands that Base can orchestrate.
• Python tools run through Base's wrapper using the base-platform-tools project virtual environment.
• Bash tools can use the Base runtime through the #!/usr/bin/env basectl pattern when they need it.

Without this structure, early tools such as future caff and sort migrations could drift into inconsistent layouts.

Scope

• Add the initial bin/, cli/bash/, and cli/python/ directory structure.
• Add placeholder documentation files that explain where Bash and Python tools belong.
• Add a documented Python launcher pattern that uses Base's base-wrapper.
• Update base_manifest.yaml with validation commands for the seeded layout.
• Update README, CONTRIBUTING, changelog, and tooling-boundary docs.
• Extend tests/validate.sh to assert the CLI scaffold and launcher conventions.

Non-Goals

• Do not migrate caff or sort yet.
• Do not add production platform tools yet.
• Do not copy basectl or base-wrapper into this repository.
• Do not change Base core behavior in this issue.

Acceptance Criteria

• The repository has a documented CLI layout for Bash and Python tools.
• Documentation clearly states that this repo reuses Base basectl and base-wrapper.
• The validation script checks the CLI scaffold and key docs.
• tests/validate.sh passes locally.
• basectl test base-platform-tools passes.