chore(release): prepare 0.12.0 - #32

Summary

Prepare 0.12.0 for the resource Search capability merged in #31. Align pyproject.toml and the uv.lock root package with 0.12.0; dependency versions are unchanged. Move the completed Search notes into the 0.12.0 changelog section and leave Unreleased empty.

Why

The next release adds typed resource filters, mandatory Search beta headers, Forward Identity query scope and POST-body cursor pagination across four Forward and eight Managed resources. This PR prepares consistent release metadata without changing the validated API implementation.

Verification

• uv sync --extra dev --extra release --locked
• uv run make lint
• uv run make typecheck
• uv run make test: 3977 passed, 73 integration tests deselected
• uv run make docs-check
• Build wheel/sdist and run twine check
• Independent wheel installation: version 0.12.0 and all four client imports
• Forward and Managed example --help smoke checks
• Changelog validation and extraction for 0.12.0
• Release automation tests
• git diff --check

CN/Global internal stable QA, Search, SA read-only, Drive, SAT management and Realtime text checks passed on the feature-source commit 5b729c3. This release PR changes only version metadata, release notes and the generated version reference where applicable. The earlier QA packages retained 0.11.0 metadata; they are not 0.12.0 release-candidate artifacts. Human QA sign-off remains pending. Channel, SA execution and Realtime PCM were not enabled.

The initial CN resources scenario failed when the model refused to return a temporary test marker; an unchanged-source rerun passed. Search passed in both regions on both runs. The original failed record is retained.

Impact

• Completed user-facing notes moved from Unreleased to 0.12.0.
• Go, Python and TypeScript release parity considered.
• No credentials, account logs or generated test artifacts committed.
• No new API, wire fixture or migration changes in this version PR; the Search implementation is already on main.
• No tag, public package or GitHub Release is created by this PR.

Coordinated version PRs: go, ts.