PDK 0.3.0

Added

• PDK installs as a command, with no clone, no git and no Python of your own: uv tool install pdk-perspective
  (the installers do it). pdk and pdk-mcp work from any folder; the schema bundle and the module build live
  under ~/.pdk/ (PDK_HOME), pulled views in work/ of the current folder. A clone works as before.
• pdk init [folder] sets up a folder for Claude Code: the perspective-views skill, the pdk-reviewer and
  pdk-log-reader subagents, the pdk MCP server in .mcp.json, the validation hook and a PDK section in
  CLAUDE.md, merged with what is there. The MCP server refreshes them after an upgrade.
• PDK says when a newer release is out: once a day it asks GitHub's public API, then tells you on the next command,
  in pdk doctor (check version) and through the MCP server, so the agent mentions it at the start of the
  session. PDK_UPDATE_CHECK=0 or update_check = false turns it off.
• pdk --version.
• Releases: a draft release follows [Unreleased] with a suggested version; publishing it tests, attaches the wheel,
  publishes to PyPI and rolls the changelog.

Changed

• The version comes from the git tag (hatch-vcs); the build backend is hatchling.
• Hints name the command as it runs on the machine (pdk ... installed, uv run pdk ... in a clone), and point to
  pdk doctor --fix for Chromium.

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Suggested from the changes since v0.2.0: v0.3.0. Publishing this draft releases it: it tags
main, attaches the wheel, publishes to PyPI and moves these notes under [0.3.0] in CHANGELOG.md.
To release another version, change the tag before publishing (vX.Y.Z).