Clarify Breeze usage in GitHub Codespaces

[bobu-putheeckal]

Summary

• clarify that Codespaces opens inside the Airflow devcontainer/Breeze environment
• remove breeze start-airflow from the Codespaces beginner flow and explain it should be run from the outer host shell with Docker socket access
• add Docker context, socket, and API-version diagnostics for Codespaces/devcontainer failures

Closes: #62405

Tests

• git diff --check
• uvx --from prek prek run rst-backticks trailing-whitespace end-of-file-fixer check-merge-conflict check-for-inclusive-language --files contributing-docs/03a_contributors_quick_start_beginners.rst contributing-docs/quick-start-ide/contributors_quick_start_codespaces.rst dev/breeze/doc/01_installation.rst
• uvx --with pygments --from docutils rst2html --halt=2 contributing-docs/quick-start-ide/contributors_quick_start_codespaces.rst /tmp/airflow-codespaces.html
• uvx --with pygments --from docutils rst2html --halt=2 dev/breeze/doc/01_installation.rst /tmp/airflow-breeze-install.html

Notes

• uv run prek ... could not start in this local environment because building jpype1==1.7.1 requires a Java runtime that is not installed.
• Standalone docutils parsing of contributing-docs/03a_contributors_quick_start_beginners.rst is not Sphinx-aware and stops on the existing :doc: role, so I validated it with the project prek hooks and git diff --check.

Was generative AI tooling used to co-author this PR?

• Yes, ChatGPT-5

Generated-by: ChatGPT-5 following the guidelines at https://github.com/apache/airflow/blob/main/contributing-docs/05_pull_requests.rst#gen-ai-assisted-contributions

[kaxil]

PR template hasn't been followed on any of your PRs. As such I am closing all your PRs since I see little to no evidence of actual testing and mass PRs to Airflow & other repos.