Run script setup dialog when no script is configured

[parsakhaz]

Problem

When no run script is configured (no DB run_script, no pane.json, no scripts/pane-run-script.js), the Play button is disabled with a "No run script configured" tooltip. Previously it silently launched Claude to generate one, which wasn't great UX either.

Proposed Solution

Show a helpful dialog when the user clicks the disabled Play button (or a nearby "Configure" link), with:

1. Explanation of how run script resolution works (the hierarchy: Project Settings > pane.json > conductor.json > .gitpod.yml > devcontainer.json > scripts/pane-run-script.js)
2. "Let Claude create one" button — launches the existing Claude-based setup flow in a terminal panel
3. Paste area for users to provide their own pane.json or conductor.json content, which Pane writes to the repo root
4. Link to docs explaining the pane.json format and config file detection

Context

This came from codex review of the pane.json PR (#107). The old behavior (silently spawning Claude with --dangerously-skip-permissions) was removed intentionally, but we need a better replacement than just a disabled button.

Dependencies

• Docs site/repository needs to exist for the docs link (see related issue)