merge: integrate main into dev

Resolve 9 merge conflicts preserving both sides' intent:
- nix hash, bootstrap hostnames rename, websocket-server wiring
- session.ts handler dedup, snapshot fallback, worktree registration
- worktree-session git service + script/setup features
- sidebar-workspace-list setup navigation, session-context cleanup
- workspace-registry-bootstrap test kept (code still exists)
- checkout-git test additions from both sides

Post-merge fixes: isPaneFocused prop rename, server type rebuild.

packages/app/src/components/workspace-setup-dialog.tsx

@@ -279,7 +279,7 @@ export function WorkspaceSetupDialog() {
         <Composer
           agentId={`workspace-setup:${serverId}:${sourceDirectory}`}
           serverId={serverId}
-          isInputActive={true}
+          isPaneFocused={true}
           onSubmitMessage={handleCreateChatAgent}
           isSubmitLoading={pendingAction === "chat"}
           blurOnSubmit={true}