feat(workflow): add WorkflowEventDispatcher + AddEscalatedWorkflows

[mpge]

Summary

Final piece of the workflow stack for .NET. Adds a decorator IEscalatedEventDispatcher that, for every event dispatched by Escalated services:

1. Forwards to the host's inner dispatcher (so host subscribers see every event in original order)
2. Resolves the event to a canonical workflow trigger name
3. Kicks WorkflowRunnerService.RunForEventAsync for matching triggers

Event → trigger mapping

Matches WorkflowEngine.TRIGGER_EVENTS:

Event	Trigger
TicketCreatedEvent	ticket.created
TicketUpdatedEvent	ticket.updated
TicketStatusChangedEvent / TicketResolvedEvent / TicketClosedEvent	ticket.status_changed
TicketReopenedEvent	ticket.reopened
TicketAssignedEvent	ticket.assigned
TicketPriorityChangedEvent	ticket.priority_changed
DepartmentChangedEvent	ticket.department_changed
TagAddedEvent / TagRemovedEvent	ticket.tagged
ReplyCreatedEvent	reply.created
SlaBreachedEvent	sla.breached
SlaWarningEvent	sla.warning

Runner failures are caught + ILogger.LogError'd so a misbehaving workflow never blocks the event that fired it.

Opt-in

Host apps wire this in once during Program.cs:

services.AddEscalated().AddEscalatedWorkflows();

AddEscalatedWorkflows() is idempotent — calling it twice doesn't double-wrap.

Complete chain

TicketService mutation
  → IEscalatedEventDispatcher.DispatchAsync
  → WorkflowEventDispatcher decorator
  → WorkflowRunnerService.RunForEventAsync
  → WorkflowEngine (conditions) + WorkflowExecutorService (actions)
  → WorkflowLog audit row

Dependencies

• Stacked on feat(workflow): add WorkflowRunnerService for event-driven workflow firing #19 (feat/workflow-runner), which is stacked on feat(workflow): add WorkflowExecutorService for action dispatch #18 (feat/workflow-executor).
• Merge order: feat(workflow): add WorkflowExecutorService for action dispatch #18 → feat(workflow): add WorkflowRunnerService for event-driven workflow firing #19 → this PR.

Test plan

• 17 xUnit tests covering event → trigger mapping (via [Theory]), inner-dispatcher forwarding, runner kick, unknown-event isolation, end-to-end workflow log creation against in-memory EF Core
• CI green (won't trigger against stacked base until rebased)