D-22: PaneManager — Tab.surface + New Dialogue Session actions

[kirich1409]

Description

Add surface: SessionSurface to Tab, wire surface selection in new-session flows, and expose keyboard shortcuts / menu entries for creating each session type.

Spec: Epic #250 §5 (mode selection UX).

Scope

File

MacApp/Packages/PaneManager/Sources/PaneManager/TabFeature.swift + menu commands in app target.

Tab changes

```swift
public struct Tab: Equatable, Identifiable, Sendable {
public var id: UUID
public var title: String
public var terminalSessionID: UUID?
public var agentSessionID: UUID?
public var worktreeID: UUID?
public var kind: SessionKind
public var surface: SessionSurface // NEW, immutable after creation
}
```

TabFeature actions

• newTab(surface:) — creates a tab with explicit surface. Defaults: shell → .shell; agent → preferredClaudeSurface from SettingsStore (see D-24).
• newDialogueSession(workingDirectory:) — convenience creating .agentDialogue(.claudeCode).
• newTerminalSession(workingDirectory:) — convenience creating .agentTerminal(.claudeCode).

UI menu entries (app target)

Update RelayApp .commands:

• ⌘T → New Tab (shell).
• ⌘⇧N → New Dialogue Session.
• ⌘⌥N → New Terminal Session.
• ⌘⇧T (per-tab) → Open as Terminal (active session).
• ⌘⇧D (per-tab) → Open as Dialogue (active session). (D-25 implements the cross-surface resume.)

Session creation sheet

If a New Session sheet UI exists (or is added as part of onboarding), it exposes a Terminal / Dialogue picker:

• Radio buttons: Terminal / Dialogue.
• Default from preferredClaudeSurface.
• Preview description per choice — single paragraph explaining difference.

Acceptance Criteria

• Tab.surface added, immutable after creation.
• newTab(surface:) action honors passed surface.
• Menu entries with shortcuts work and create correct session type.
• New Session sheet (if extended) shows Terminal / Dialogue picker.
• Existing shell / terminal tests unaffected (regression green).
• Persisted tab state (if any) migrates: missing surface fields default to .shell for shell tabs, .agentTerminal(.claudeCode) for agent tabs.

Relationships

• Parent issue: EPIC: Dialogue — structured chat UI for agent sessions #250
• Blocked by: #D-21, D-6: SharedModels — introduce SessionSurface enum #256 (SessionSurface)
• Blocks: #D-23 (view routing), #D-25 (Open as X)