fix: a demo repo's SOPS value can be the share key

The demo provider finds repos by their remote, as the repo provider
does, so a key in a demo repo's SOPS file can be read. Opening a
share link uses the repo's clone only when it's on disk (the demo's
aren't), else asks where to save. The demo GitHub client secret is 40
characters, like real ones, so it passes share.keyRules.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

internal/provider/fake/repos.go

@@ -94,7 +94,7 @@ func Repos() *Provider {
 		"database.url", "postgres://app:stg-Pg-2b8d1L@pg-demo-stg:5432/app",
 		"stripe.secret_key", "sk_test_demo_51NxDemoKey0000")
 	file(api, "config/oauth.enc.json", "age", "tracked", "e03b6f1 · 2 months ago",
-		"github.client_secret", "ghs_demo0000000000000000000000",
+		"github.client_secret", "8f3c2a9d7e1b6f4a0c5d2e9b8a7f6c3d1e0b4a5f",
 		"google.client_secret", "GOCSPX-demo-000000000000")
 	file(api, ".env", "", "ignored", "",
 		"DATABASE_URL", "postgres://app:local@localhost:5432/app",