Expand STANDARDS.md for Base architecture and Python CLIs

[codeforester]

STANDARDS.md is still mostly inherited from the earlier Bash-focused version of Base. Current Base has a clearer layered architecture and Python CLI conventions that should be captured as contributor standards.

Scope:

1. Keep the existing Bash standards, but make them part of a broader Base contributor standard.
2. Add Base architecture/layering standards: basectl control plane, Bash bootstrap/runtime layer, Python manifest/project layer, base-wrapper, public bin/ surface, and project venv boundaries.
3. Add Python standards: PEP 8-oriented style, from __future__ import annotations, pathlib.Path, dataclasses where useful, explicit main(argv) -> int, base_cli.App, ctx.log, structured JSON through json.dumps, no import-time side effects beyond command registration.
4. Make it explicit that Python CLIs intended for direct execution should use base-wrapper in the shebang so they run in the selected project virtual environment.
5. Add a short “where does this code belong?” table to guide future contributors.
6. Add CLI behavior, manifest/artifact, testing, documentation, and GitHub workflow standards at a concise level with links to deeper docs.

Acceptance criteria:

• STANDARDS.md covers Bash, Python, CLI behavior, layering, manifests, testing, docs, and GitHub workflow.
• The base-wrapper shebang convention for Python CLIs is explicit.
• The document remains readable and normative rather than becoming a long design essay.
• The PR is documentation-only unless a tiny supporting reference update is needed.