chore(release): promote to [6.6.2] — fix shipped __version__ runtime drift

[saurabhjain1592]

Summary

Patch release to fix a real bug in the shipped v6.6.1 wheel: axonflow.__version__ at runtime returns "6.6.0" even though pip show axonflow correctly reports 6.6.1.

Three changes:

• CHANGELOG.md: new ## [6.6.2] - 2026-04-25 section
• pyproject.toml: 6.6.1 → 6.6.2
• axonflow/_version.py: 6.6.1 → 6.6.2

All three move together so the validate-version-alignment gate stays green through the transition.

Root cause (now fixed)

release.yml was running:

sed -i "s/^__version__ = .*/__version__ = \"${VERSION}\"/" axonflow/__init__.py

But axonflow/__init__.py only does from axonflow._version import __version__. The sed matched nothing and silently exited 0. The real __version__ constant lives in axonflow/_version.py which was never touched during release. Result: every published wheel had axonflow/_version.py frozen at whatever value was on main before the tag was pushed.

Fix landed in #153 (merged earlier today) — release.yml now seds _version.py and asserts-post-sed so silent no-ops fail loudly. v6.6.2 is the first release to benefit from that fix.

What v6.6.2 changes for users

Functional behavior: none. Same SDK as v6.6.1.

Observable: axonflow.__version__ now correctly returns "6.6.2". Affects:

• Telemetry self-reporting (your adoption metrics show accurate numbers)
• User code doing version-gated feature detection (if axonflow.__version__ >= "6.6.1") — was broken on v6.6.1, works on v6.6.2
• Log output / bug reports that print SDK version

Impact assessment on other SDKs

Full audit done before this PR. The bug is Python-only — it was specific to the two-file _version.py + __init__.py setup where release.yml was targeting the wrong file:

SDK	Latest	Status
Python	6.6.1 → 6.6.2 (this PR)	was broken, being fixed
Go	v5.6.1	version.go = 5.6.1 ✓
TS	5.6.0	package.json + both dist/*/version.js all at 5.6.0 ✓
Java	5.7.0	pom.properties in JAR reads 5.7.0 (consumed at runtime via detectSdkVersion()) ✓

Release flow after merge

1. Merge this PR
2. Tag v6.6.2
3. release.yml preflight validates CHANGELOG section matches tag
4. Build + publish to PyPI via trusted publisher
5. Verify: pip install axonflow==6.6.2 && python -c "import axonflow; print(axonflow.__version__)" returns "6.6.2"

Test plan

• validate-version-alignment.sh passes locally
• Release-workflow awk extracts [6.6.2] section cleanly
• CI green on this PR
• Post-publish: runtime __version__ matches tag