[codex] Add 0.6 release notes

[k82cn]

Summary

Add release notes for Flame 0.6.0 under docs/releases/v0.6.0.md.

The notes track the final source tag v0.6.0 at 12432449a82079a7773ea833f2a9ac15d9ce3c3f, which matches the release-0.6 snapshot previously tagged v0.6.0-rc2, and summarize the changes from v0.5.0 through v0.6.0.

Notes

• This PR is intentionally release-notes only.
• The compare link points to v0.5.0...v0.6.0.
• The notes include the release-prep work merged through Backport PR #488 to release-0.6 #489, including Python package metadata, Kubernetes/Helm release updates, CLI version metadata, Rust SDK publish metadata, and Python Runner E2E coverage.
• The release status now documents the published stable flamepy 0.6.0, flame-rs-macros 0.6.0, flame-rs 0.6.0, and multi-arch Docker v0.6.0 image tags for linux/amd64 and linux/arm64.
• The versioned source, PyPI, Rust crate, and Docker v0.6.0 artifacts no longer have a documented publication gap; latest has not been moved.

Validation

• Verified on June 4, 2026 that PR [codex] Add 0.6 release notes #476 is open, merge-clean, and targets release-0.6.
• Fetched upstream tags and confirmed upstream v0.6.0 resolves to 12432449a82079a7773ea833f2a9ac15d9ce3c3f, matching upstream/release-0.6.
• Confirmed the branch diff against release-0.6 only adds docs/releases/v0.6.0.md.
• Ran git diff --check upstream/release-0.6...HEAD.
• Reverified current Docker artifact status with Podman: final Docker v0.6.0 tags are published for all four images and expose linux/amd64 plus linux/arm64.
• Earlier post-release sanity checks passed for PyPI import of flamepy==0.6.0, fresh Cargo crate cargo check with flame-rs@0.6.0 --features macros, and pull/run checks for all four arm64 Docker tags.
• Pushed head f23fb53e.

[gemini-code-assist]

Code Review

This pull request adds the release notes for Flame version 0.6.0, which detail major highlights, upgrade instructions, SDK updates, and other improvements. Feedback was provided regarding an inconsistency where the release notes state that the Python SDK requires Python 3.9 or newer, but the pyproject.toml configuration file still references Python 3.8 in its classifiers and mypy settings.

[gemini-code-assist]

The release notes state that the Python SDK requires Python 3.9 or newer. However, sdk/python/pyproject.toml still contains references to Python 3.8 in the classifiers (Programming Language :: Python :: 3.8 on line 21) and the mypy configuration (python_version = "3.8" on line 86). Please update sdk/python/pyproject.toml to remove these Python 3.8 references to ensure consistency with the new Python 3.9+ requirement.

[k82cn]

The amd64 was pushed, let's update accordingly.