docs: update deprecated key_value.shared references

[github-actions]

This updates documentation to reflect the key_value.shared deprecation and module move introduced in key_value.__init__.

What changed

• Updated CODE_STYLE.md to reference key_value.aio._utils.managed_entry.
• Updated docs/adapters.md examples to import errors from key_value.aio.errors.
• Updated DEVELOPING.md project structure to show aio/_utils and aio/errors instead of shared/.

Validation

• UV_CACHE_DIR=/tmp/gh-aw/agent/uv-cache make test-concise ✅ passed
• UV_CACHE_DIR=/tmp/gh-aw/agent/uv-cache make lint ⚠️ fails on pre-existing unrelated Ruff issues in tests/stores/elasticsearch/test_elasticsearch.py (SIM118 x2)

Issue context: #321

• Fixes [docs-drift] Update docs for key_value.shared deprecation and package move #321

AI generated by Issue Assistant

[macroscopeapp]

Update documentation to replace deprecated key_value.shared references with key_value.aio paths across CODE_STYLE, DEVELOPING, and adapters docs

Refreshes docs to use key_value.aio._utils.managed_entry for ManagedEntry and moves error imports to key_value.aio.errors; updates the project structure section to reflect key_value/aio/_utils and key_value/aio/errors.

📍Where to Start

Start with the updated import guidance in CODE_STYLE.md, then review structure changes in DEVELOPING.md, and finish with example imports in docs/adapters.md.

Changes since #323 opened

• Updated exception class import in RaiseOnMissingAdapter documentation example [c098a2d]

---

Macroscope summarized 4af0d38.