fix(subagents): honor approval-pause in every tool-watchdog mode

[Aaronontheweb]

What & why

Step 1 of #1472. A human-approval block sets ToolActivityUpdate.SuspendsInactivityWatchdog to pause the per-tool-call liveness clock. The tool-liveness change gated that suspend behind ResetMode != WallClock, so in WallClock mode (every opaque tool) the approval-pause was ignored and the wall-clock budget kept ticking through a human approval — killing a healthy tool mid-approval whenever the human took longer than the budget.

This violated the intended contract: approvals (and any explicit human-block) must never affect the wall clock, in any mode.

The fix

StreamingToolWatchdog.cs — honor SuspendsInactivityWatchdog in all modes. The change is surgical: ordinary per-item resets stay mode-gated in ApplyItemReset (WallClock still can't be kept alive by its own streamed output); only the explicit human-block signal is now universal.

- if (budget.ResetMode != ToolWatchdogResetMode.WallClock && activity.SuspendsInactivityWatchdog)
+ if (activity.SuspendsInactivityWatchdog)
      Volatile.Write(ref budgetTicks, TimeSpan.Zero.Ticks);

Test (the part that lets it regress)

The pre-existing suspend test only exercised Flat mode — which is exactly why the WallClock regression slipped through. Replaced with a mode-matrix [Theory] across Flat / FirstItemOnly / WallClock. Verified as a real guard:

• old guard restored → wallClock FAILS, flat/firstItemOnly pass
• fix applied → all three pass

Scope

Targeted fix only — deliberately small and shippable independent of the larger consolidation. The structural rework (collapse to one actor-owned watchdog, approval-as-state, kill the silent ?? Opaque, etc.) is tracked as the migration steps in #1472.

Relates to #1467. Part of #1472.

[Aaronontheweb]

LGTM