Add app icon at repo-root favicon.svg for Conductor

[fredrivett]

Adds a top-level favicon.svg so Conductor can find and display reeve's app icon.

Of Conductor's search paths, no public/ directory exists (reeve is a Swift package, not a web app), so the repo-root favicon.svg is the highest-priority path that fits this layout. The icon reuses the existing brand mark from site/favicon.svg (the grey rounded-square "r" logo), which scales cleanly at any size.

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Summary by cubic

Add a repo-root favicon.svg so Conductor can find and display reeve’s app icon. Reuses the site/favicon.svg gray rounded-square “r” mark, placed at the top level since this Swift package has no public/ directory.

^{Written for commit 682c441. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}