Adding .NET SDK documentation for history propagation

[WhitWaldo]

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Description

Added .NET SDK documentation for workflow history propagation functionality

Issue reference

[github-actions]

Auto-approval: dotnet SDK docs

[github-actions]

Auto-approval: dotnet SDK docs

[nelson-parente]

Pre-review for @marcduiker handoff: LGTM. New .NET SDK page for workflow history propagation. Content is well-structured: scopes table, propagating to child workflows, propagating to activities, reading history, and the PropagatedHistory type. Code examples use correct API surface (WithHistoryPropagation, HistoryPropagationScope, GetPropagatedHistory()). Version note (Dapr .NET SDK v1.18 + runtime v1.18) is present. Hugo front-matter looks good. Safe to merge after CI.

[WhitWaldo]

@marcduiker Going to mark this as a do-not-merge momentarily as it needs updating to reflect another PR @nelson-parente opened that addresses some shortcomings in the first pass of this implementation.

[github-actions]

Auto-approval: dotnet SDK docs

[msfussell]

LGTM

[github-actions]

Auto-approval: dotnet SDK docs

[cicoyle]

lgtm but CI is 🔴 Mind taking a look @WhitWaldo ?

[WhitWaldo]

@cicoyle Nelson is still wrapping up the revised implementation, so these documents are probably out of date. After his PR is merged, I'll update these docs and figure out why CI is unhappy.