The toolbar on a public app that is not yours says Make it yours, and one tap forks it into your forge #11463

Intent: vision, P6: "make it yours" from wherever you are.

Done:

• [ ] src/apps/toolbar.ts adds one link, "Make it yours", for a reader who is signed in and does not own the app, pointing at the forge's existing fork-this-app page for that app (no new route; read the app page's make-it-yours first)
• [ ] a signed-out reader's link goes through the existing sign-in and comes back; the owner and a private app show no link
• [ ] no layout shift: it sits in the closed shadow root as the rest does; app names travel as escaped data attributes; the CSP is unchanged
• [ ] tests: link present for a signed-in stranger on a public app, absent for the owner, a private app and JSON/asset responses; docs/features/forge-toolbar.md names it

Files: src/apps/toolbar.ts, src/apps/proxy.ts only if it must pass who the reader is (never trust the client's word for it), test, docs. Risks: #11434 also edits the toolbar's text; rebase on whichever lands first. Suggested brief: scout.