conformance.md opt-out example instantiates the static FeatureSet class

[nficano]

Category: docs Severity: major
Location: docs/conformance.md:60-65

What

FeatureSet is a static class (src/Arcp.Core/Capabilities/Capabilities.cs:79) with no constructor, and ArcpClientOptions.Features is IReadOnlyList? (src/Arcp.Client/ArcpClientOptions.cs:21). new FeatureSet([...]) cannot compile.

Evidence

new ArcpClientOptions
{
    Features = new FeatureSet(["heartbeat", "ack"]), // drop the rest
};

Proposed fix

Use Features = new[] { FeatureFlags.Heartbeat, FeatureFlags.Ack } as sessions.md does.

Acceptance criteria

• The example assigns a string list to Features and compiles.