.NET: Fix declarative resume edge predicates to recognize both direct and PortableValue-wrapped forms after checkpoint restore

[peibekwe]

Motivation and Context

After a JSON checkpoint round-trip, queued messages are restored as PortableValue wrappers. Edge predicates in evaluate Message directly, so predicates like RequiresInput and RequiresNothing fail to match path.

Fixes #5307

Description

• Update impacted declarative edge predicates to handle PortableValue. Also harden ActionExecutorResult to unwrap PortableValue as a second line of defense once a message reaches the target executor path.
• Added relevant unit tests.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull request overview

Fixes declarative workflow resume routing after JSON checkpoint restore by ensuring edge predicates and executor result handling recognize PortableValue-wrapped messages, preventing mismatched transitions and “no handler found” failures.

Changes:

• Updated declarative edge predicates (RequiresInput / RequiresNothing) to match both direct messages and PortableValue-wrapped equivalents.
• Hardened ActionExecutorResult.ThrowIfNot to unwrap PortableValue-wrapped ActionExecutorResult instances.
• Added unit tests covering predicate behavior and ThrowIfNot unwrapping/throwing scenarios.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/ObjectModel/InvokeAzureAgentExecutor.cs	Makes routing predicates tolerant of PortableValue-wrapped ExternalInputRequest / ActionExecutorResult.
dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/ObjectModel/InvokeMcpToolExecutor.cs	Aligns MCP tool executor routing predicates with checkpoint-restored PortableValue wrappers.
dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/Kit/ActionExecutorResult.cs	Unwraps PortableValue in ThrowIfNot as a defensive backstop when messages reach executors.
dotnet/tests/Microsoft.Agents.AI.Workflows.Declarative.UnitTests/Kit/PortableValuePredicateTests.cs	Adds targeted unit coverage for PortableValue predicate matching and result unwrapping behavior.