Clarify directory review context and remove redundant CLAUDE.md

[georgeatparallel]

Claude's directory flags the root CLAUDE.md because it is not loaded when the plugin is installed:

CLAUDE.md at the plugin root is not loaded as project context. To ship context with your plugin, use a skill (skills/<name>/SKILL.md) instead.

The file only repeats that limitation and points to the skills and agents. Remove it; it contains no development instructions or installed plugin behavior.

Also clarify the README's credential disclosure: the bundled MCP is anonymous, CLI skills authenticate separately to Parallel, and migration examples and synthetic scanner fixtures do not run when the plugin loads. Authentication and onboarding behavior are unchanged. This explanation helps reviewers assess the remaining credential holds; it does not claim to clear them.

Set documentationUrl to https://docs.parallel.ai/home so the directory links to Parallel documentation instead of inferring Claude's generic plugin guide from the README.

The documentation URL update passes Claude plugin validation and git diff --check.

Earlier validation: 37 Python tests pass, git diff --check passes, and Claude plugin validation passes without the root-file warning.

Portal warning before this change: