README copy trims: drop redundant H1 and stdlib parenthetical

[danielrmay]

Summary

• Removes the # Claudity H1; the hero GIF's own wordmark header makes it redundant.
• Removes the "(the bundled scripts are stdlib-only, nothing to pip install)" parenthetical from the install requirements line.

Test plan

• Rendered markdown eyeballed; no structural changes beyond the two deletions.