chore(release): prepare v0.3.0

[fancyboi999]

Summary

• finalize the cumulative 0.3.0 changelog for every merged change since v0.2.4
• set the actual release date to 2026-08-19
• synchronize uv.lock with the already-merged mcp>=1.2,<2 runtime constraint

Why

The repository and all plugin manifests already target 0.3.0, while PyPI remains on 0.2.4 and no v0.3.0 tag exists. This prepares the exact release commit before publishing PyPI and the ClawHub bundle.

Verification

• uv run python -m pytest — 185 passed
• uv run ruff check src tests scripts
• uv run python scripts/check_sensitive_identifiers.py
• uv build; wheel metadata reads Version: 0.3.0 and Requires-Dist: mcp<2,>=1.2
• MCP initialize + tools/list from the built wheel via temporary uvx — 17 tools
• pnpm dlx npm@10.9.2 test — 3 passed
• pnpm dlx npm@10.9.2 run pack:check — 33 files, content scan clean
• git diff --check

Release boundary

PR #21 remains a separate changes-requested bug fix and is not included in this release-prep diff.