GeezerVison

Each right panel component has a single production caller (AgentChatPageView, GitPanel, CommentableDiffViewer, DebugPanel, DebugRunCard, DebugStepCard), and those callers always pass these props. That made the optional types, defaults and guards dead. TerminalPanel is only rendered behind workspace && workspaceAgent, so its "agent not ready" fallback could never render. DebugStepCard.defaultOpen was always false, so the prop is removed. DebugRunCard no longer needs its own download = saveAs default, because DebugPanel owns that default and always forwards download.

This change makes the following props required: isExpanded/chatInputRef through GitPanel → RemoteDiffPanel/LocalDiffPanel → CommentableDiffViewer → DiffViewer, plus DiffViewer's line callbacks and annotationsVersion's input; GitPanel.isGitStatusLoading/everDirty; TerminalPanel.workspace/workspaceAgent/isHot/autoFocus/onReady; DesktopPanel.isVisible and DesktopPanelView.onPopOut; RightPanelAddTabControl.host/isRunning/onOpenWorkspaceApp/onOpenCommandApp/onOpenPort; DebugPanel.isVisible; DebugRunList/DebugRunCard.download; PillToggle.count; ToolEventCard.copyLabel; and debugExportFilename's exportedAt. The DiffViewer, GitPanel and TerminalPanel stories now pass the required args. The TerminalPanel AgentUnavailable story and the annotationsVersion(undefined) assertion are removed because production cannot reach them. These stay optional on purpose: DebugPanel.download (a test injection point that defaults to saveAs), DesktopToolbar.onPopOut (the pop-out page omits it), and LocalRepoContent.repo (it comes from Map.get).

Part of the AgentsPage nullability cleanup; see #29888 for the methodology. Dead slots in the right panel cluster: 39 before, 0 after.

This PR was generated by Coder Agents on behalf of @DanielleMaywood.