Add a share-safe export and screenshot mode

[raphant]

Goal

Let users share a session view without exposing sensitive prompts, paths, commands, ticket details, or credentials.

Proposed change

Add a local redaction preview before any screenshot or recording export.
Provide default rules for home paths, repository paths, issue identifiers, command arguments, and credential-shaped text.

Acceptance criteria

• Share-safe mode previews every replacement before export.
• The export defaults to deny when content cannot be classified safely.
• Users can add local literal or regular-expression rules.
• Redaction applies to canvas labels, panels, transcripts, and exported recordings.
• Tests include paths, tokens, connection strings, multiline commands, and false positives.

Source

• web/components/agent-visualizer/transcript-message.tsx renders transcript content.
• web/components/agent-visualizer/tool-detail-popup.tsx renders tool arguments and results.