feat(dispatch): attach-all in grid mode + project terminal setting

[Juliusolsson05]

Two related dispatch polish fixes in one PR.

Part A — Attach All Dispatch Agents For Tab works in grid mode

The command was gated by dispatchCommandTabId, which returns null whenever the workspace is not in Dispatch. That forced users with parked agents to first flip into Dispatch just to bring them back into the grid — friction with no upside.

Replaced with attachAllCommandTabId:

• In Dispatch: delegate to dispatchCommandTabId so global Dispatch can still target the focused row's tab (which may differ from activeTabId).
• Outside Dispatch: fall back to state.activeTabId. The command appears whenever the active tab has detached agents waiting.

attach-detached-to-grid (the single-agent picker) stays dispatch-only — it needs a dispatch-focused session as its target, so there is no clean grid-mode meaning.

Part B — Dispatch project terminal is a setting, off by default

The dispatch terminal was gated by an ephemeral dispatchMode.terminalVisible flag in workspace state. That flag re-defaulted to ON every time Dispatch was re-entered (fresh workspace, new tab, scope switch) — the "I turned it off but it came back" failure mode the user has been hitting.

• New settings.dispatchProjectTerminal: boolean in app-state/settings/types.ts, default false, coerced strictly (=== true) so missing/malformed values stay off.
• New entry in Settings → Workspace: "Attach Project Terminal to Dispatch".
• DispatchLayout reads the setting and conditionally mounts the terminal pane + claims layout space. When OFF the agent panel takes basis-full.
• Removed toggleDispatchTerminal action + the toggle-dispatch-terminal command (per the user request: "settting defined in settings, not a command").
• Dropped terminalVisible from DispatchModeState; older workspace.json entries with the field are harmlessly ignored.
• enterDispatchMode / setDispatchScope no longer call ensureDispatchTerminal themselves. The DispatchLayout useEffect is the only spawn site now, gated by the setting — so flipping the setting OFF and re-entering Dispatch cannot silently spawn a fresh terminal.

Test plan

• In grid mode, with detached agents parked, open command palette → "Attach All Dispatch Agents For Tab" runs and pulls them into the active tab's grid.
• Fresh workspace + enter Dispatch → no terminal pane visible; agent panel is full-width.
• Flip Settings → Workspace → "Attach Project Terminal to Dispatch" ON → terminal pane appears within a frame.
• Flip it OFF → pane disappears; the terminal session itself is not killed (it remains as a normal tile-tree leaf in the tab and can be closed like any other pane).
• Restart the app → setting persists; terminal does not auto-spawn behind the user's back.

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