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/panels/agent-panel.tsx

@@ -965,7 +965,7 @@ function ChatAgentContent({
             <Composer
               agentId={agentId}
               serverId={serverId}
-              isInputActive={isPaneFocused}
+              isPaneFocused={isPaneFocused}
               value={agentInputDraft.text}
               onChangeText={agentInputDraft.setText}
               images={agentInputDraft.images}