docs: align Base ecosystem platform, license, and release-policy contracts

[codeforester]

Goal

Align base-cli's public documentation and release workflow with the canonical Base ecosystem policy.

Background

The parent cross-repository policy issue is basefoundry/base#2116. Base owns the coordinated release matrix and BOM; base-cli remains an independently released framework with its own broader platform support.

Scope

• Link the README, platform-support documentation, and release guide to the canonical Base policy.
• Correct the stale Base license statement.
• State that native Windows and WSL2 support for the generic framework does not imply native Windows or WSL2 support for Base.
• Make published tags and release assets immutable by refusing to replace an existing GitHub Release.
• Keep the change documentation and release-workflow focused.

Acceptance Criteria

• Current docs contain no stale AGPL claim about Base.
• The component/platform boundary and Base's Ubuntu 24.04/macOS 14 release matrix are explicit.
• The package workflow does not use --clobber for published release assets.
• Focused workflow tests and diff checks pass.

Validation

• .venv/bin/python -m pytest -q tests/test_package_workflow.py
• git diff --check

Non-Goals

• Do not change base-cli's own supported framework matrix.
• Do not make a Base release or change the Base BOM.

Project Fields

• Status: Backlog
• Priority: P2
• Size: S
• Area: Docs
• Initiative: Adoption Polish

Ownership

• Assignee: @codeforester

Parent: basefoundry/base#2116

[codeforester]

Closed after companion PR #337 merged. The ecosystem platform, license, and immutable release-policy documentation is aligned with Base #2116.