[iamnbutler]

Part of #636. Map ids: ^106 ^115.

After this Mac left a directory that a teammate's host still serves, the sidebar card used to offer Create directory.

• The host now remembers the directory each peer's hello names (directory.offer), and drops it when the peer goes away or stops naming one.
• A host with no directory keeps greeting peers on each discovery pass so that list stays current. Leaving still counts as a choice: adopt never joins on its own after a choice.
• Diagnostics report directory.offered (url and host) while this host has no directory.
• When something is offered, the sidebar card says " serves your team's directory…" and shows Join, which runs directory-set with that URL, and Change…, which opens Settings → Team.
• The offline-channel panel no longer claims "Your team has no directory" when a teammate serves one.

Checks: bun types, bun run ci.

Not live-tested: the card needs a real teammate host that serves a directory. The only one is another person's Mac, and reaching it from an isolated host would have meant using the real Ace's peer port on this Mac. I stopped that attempt, so the Join and Change paths in this state haven't been run end to end.

Built in Ace

No. This was made from Claude Code as a fix-train worker, outside Ace. Dogfooding gap tracked in #5.