Throw ObjectNotFoundException from FindRequired; add run-console wrappers

- DbBase.FindRequired / Client.FindByNameRequired now throw the
  domain-specific ObjectNotFoundException (NHibernate lineage; Rails
  equivalent: ActiveRecord::RecordNotFound) on a lookup miss; the
  no-context case stays InvalidOperationException (configuration error)
- Console demo catches the new type; tests (18)/(21) assert it,
  (19)/(23) keep InvalidOperationException with rationale comments
- scripts/run-console.sh delegates to dotnet.sh; run-console.ps1 is
  the Windows/PowerShell counterpart (mise-first, repo-root cd)

Yak: objectnotfoundexception-run-console-wrappers-3p8b

src/Before.Console/Program.cs

@@ -44,9 +44,6 @@ foreach (var client in DbBase.Context!.Tracked.OfType<Client>())
 // ----- find by name -------------------------------------------------------
 Console.WriteLine("\n=== Find by Name (null-returning) ===");
 // No context argument: FindByName falls back to the DbBase.Context singleton.
-// This is the ActiveRecord ergonomic — call sites don't carry the context,
-// but the null that comes back on a miss can't tell "no such client" from
-// "nobody configured the context".
 var found = Client.FindByName("Jane Doe");
 if (found is not null)
 {
@@ -66,7 +63,7 @@ try
     Console.WriteLine($"Found: {required.Name} [{required.Id}]");
     Console.WriteLine($"  Orders: {required.Orders.Count}");
 }
-catch (InvalidOperationException ex)
+catch (ObjectNotFoundException ex)
 {
     Console.WriteLine($"Not found: {ex.Message}");
 }
@@ -79,7 +76,7 @@ try
 {
     Client.FindByNameRequired("Nobody Here");
 }
-catch (InvalidOperationException ex)
+catch (ObjectNotFoundException ex)
 {
     var msg = ex.Message.ReplaceLineEndings(" ").Trim();
     Console.WriteLine($"FindByNameRequired(\"Nobody Here\"): throws - {msg}");

src/Before/Client.cs

@@ -43,9 +43,10 @@ public class Client : DbBase
 
     /// <summary>
     /// Throwing variant of <see cref="FindByName(string,DbContext?)"/>.  Returns
-    /// the matching <see cref="Client"/> or throws <see cref="InvalidOperationException"/>
-    /// with a message that includes the searched <paramref name="name"/> and
-    /// whether a context was configured.
+    /// the matching <see cref="Client"/> or throws <see cref="ObjectNotFoundException"/>
+    /// with a message that includes the searched <paramref name="name"/>.
+    /// Throws <see cref="InvalidOperationException"/> instead when no context at all
+    /// is configured (a configuration error, not a lookup miss).
     ///
     /// Delegates to <see cref="DbBase.FindRequired{T}"/>.
     /// </summary>
@@ -53,8 +54,11 @@ public class Client : DbBase
     /// <param name="db">The context whose tracked entities to search. When
     /// <c>null</c>, falls back to the <see cref="DbBase.Context"/> singleton.</param>
     /// <returns>The first client whose <see cref="Client.Name"/> equals <paramref name="name"/>.</returns>
+    /// <exception cref="ObjectNotFoundException">
+    /// Thrown when no matching client is found.
+    /// </exception>
     /// <exception cref="InvalidOperationException">
-    /// Thrown when no matching client is found or no context is configured.
+    /// Thrown when no context is configured (neither passed explicitly nor set as the singleton).
     /// </exception>
     public static Client FindByNameRequired(string name, DbContext? db = null)
         => DbBase.FindRequired<Client>(c => c.Name == name, db, $"name == \"{name}\"");

src/Before/DbBase.cs

@@ -86,8 +86,9 @@ public class DbBase
     /// <summary>
     /// Throwing variant of <see cref="Find{T}(System.Predicate{T},DbContext?)"/>.  Finds the first entity
     /// whose runtime type matches <typeparamref name="T"/> and satisfies
-    /// <paramref name="predicate"/>.  Throws <see cref="InvalidOperationException"/>
-    /// when no match is found or when no <see cref="Context"/> singleton is configured.
+    /// <paramref name="predicate"/>.  Throws <see cref="ObjectNotFoundException"/>
+    /// when no match is found, and <see cref="InvalidOperationException"/> when no
+    /// <see cref="Context"/> singleton is configured (a configuration error, not a lookup miss).
     ///
     /// The exception message includes <paramref name="predicateToString"/> so
     /// callers can debug which lookup failed.
@@ -98,8 +99,11 @@ public class DbBase
     /// <param name="predicateToString">A human-readable description of the predicate, used in the
     /// exception message when the search fails.</param>
     /// <returns>The first matching entity.</returns>
+    /// <exception cref="ObjectNotFoundException">
+    /// Thrown when no entity matches <paramref name="predicate"/>.
+    /// </exception>
     /// <exception cref="InvalidOperationException">
-    /// Thrown when no entity matches <paramref name="predicate"/> or when no context is available.
+    /// Thrown when no context is available (neither passed explicitly nor set as the singleton).
     /// </exception>
     public static T FindRequired<T>(Predicate<T> predicate, DbContext? db, string predicateToString)
         where T : DbBase
@@ -117,7 +121,7 @@ public class DbBase
             if (e is T candidate && predicate(candidate))
                 return candidate;
 
-        throw new InvalidOperationException(
+        throw new ObjectNotFoundException(
             $"FindRequired<{typeof(T).Name}>({predicateToString}) — " +
             $"no matching {typeof(T).Name} found in context.");
     }

src/Before/ObjectNotFoundException.cs

@@ -0,0 +1,17 @@
+namespace Before;
+
+/// <summary>
+/// Thrown when a "required" ActiveRecord-style lookup —
+/// <see cref="DbBase.FindRequired{T}"/> / <see cref="Client.FindByNameRequired"/> —
+/// finds no matching entity in the context.
+///
+/// Named after NHibernate's <c>ObjectNotFoundException</c> (Rails' ActiveRecord
+/// raises <c>ActiveRecord::RecordNotFound</c> for the same situation), so a
+/// lookup miss is distinguishable from unrelated
+/// <see cref="InvalidOperationException"/>s such as EF's <c>Single()</c>
+/// "Sequence contains no elements".
+/// </summary>
+public class ObjectNotFoundException : Exception
+{
+    public ObjectNotFoundException(string message) : base(message) { }
+}