docs: embed the rendered class diagram in the timeout README

Render etc/timeout.urm.puml to PNG and embed it in the detailed explanation section, matching the other modules, instead of the inline mermaid block.

Author: ylcn91

timeout/README.md

@@ -59,6 +59,8 @@ sequenceDiagram
     end
 ```
 
+![Timeout class diagram](./etc/timeout.urm.png)
+
 ## Programmatic Example of Timeout Pattern in Java
 
 The example models an online shop that calls two downstream services. The product catalog is fast; the recommendation engine is slow. Each gets its own time limit.
@@ -205,57 +207,6 @@ Timeouts per service: {recommendations=1}
 
 The "exceeded its 100 ms limit" line is written by the caller and the "interrupted, abandoning" line by the worker thread, so the two may appear in either order from run to run.
 
-## Class Diagram
-
-```mermaid
-classDiagram
-    class TimeoutPolicy {
-        <<record>>
-        +String serviceName
-        +Duration timeout
-        +of(serviceName, millis)$ TimeoutPolicy
-    }
-    class TimeoutMetrics {
-        -ConcurrentMap~String, AtomicInteger~ timeouts
-        +recordTimeout(serviceName) void
-        +timeoutCount(serviceName) int
-        +snapshot() SortedMap~String, Integer~
-    }
-    class TimeoutExecutor {
-        -ExecutorService executor
-        -TimeoutMetrics metrics
-        +execute(policy, call, fallback) T
-        +metrics() TimeoutMetrics
-        +close() void
-    }
-    class ServiceCallException {
-        +ServiceCallException(serviceName, cause)
-    }
-    class DownstreamService {
-        -String name
-        -Duration latency
-        -List~String~ items
-        +name() String
-        +fetch() List~String~
-    }
-    class App {
-        -List~String~ POPULAR_ITEMS$
-        +main(args)$ void
-        ~call(executor, policy, service, fallback)$ List~String~
-    }
-
-    ServiceCallException --|> RuntimeException
-    TimeoutExecutor --> TimeoutMetrics : counts timeouts in
-    TimeoutExecutor ..> TimeoutPolicy : reads the limit from
-    TimeoutExecutor ..> ServiceCallException : throws
-    App ..> TimeoutPolicy : configures
-    App ..> TimeoutExecutor : calls through
-    App ..> TimeoutMetrics : reports
-    App ..> DownstreamService : calls
-```
-
-The same diagram is kept as PlantUML in [timeout.urm.puml](./etc/timeout.urm.puml).
-
 ## When to Use the Timeout Pattern in Java
 
 * Whenever a call leaves the process: HTTP and gRPC calls, database queries, message broker round trips, third-party APIs.