Add entire-powered commit-push-pr skill, bump to v0.4.0

New skill at skills/commit-push-pr/SKILL.md that mines entire explain --commit <sha> --short --no-pager for every commit in the push range to synthesize the PR title and body, with a silent fallback to a git-only flow when no commit in the range is checkpoint-backed. Caps per-commit lookups at 10 and uses a single entire dispatch --local --since for larger ranges. Always opens the PR as --draft, updates an existing open PR via gh pr edit instead of creating a duplicate, and never uses entire search (server-indexed, missing local checkpoints) or git add -A/git add ..

README adds a section for the new skill, two natural-language Quick Start triggers, and a cross-reference to the upstream commit-commands:commit-push-pr for users without Entire history.

Bumps the version from 0.3.0 to 0.4.0 across all six versioned manifests (package.json, gemini-extension.json, .claude-plugin/{plugin, marketplace}.json, .codex-plugin/plugin.json, .cursor-plugin/plugin.json) and updates the pinned tag in .opencode/INSTALL.md to match.