fix: SwitchToAsync compat with local SDK build

[PureWeen]

One-line fix: removes the extra null arg from SwitchToAsync so it compiles against the local SDK (3-arg signature) instead of only v0.2.2 (4-arg with ModelCapabilitiesOverride).

[PureWeen]

🔍 Multi-Model Code Review — PR #647

Reviewed by: Direct review (1-line diff, no sub-agent dispatch needed)
Diff reviewed: +1/−1, 1 file
CI Status: ⚠️ Expert Code Review pending

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Findings

🟡 MODERATE — #1: Breaks published SDK v0.2.2 build

File: CopilotService.cs, line 3316

The PR removes the null argument for ModelCapabilitiesOverride? from SwitchToAsync:

// Before (4-arg, matches SDK v0.2.2):
await state.Session.Rpc.Model.SwitchToAsync(normalizedModel, reasoningEffort, null, cancellationToken);

// After (3-arg, matches local SDK build):
await state.Session.Rpc.Model.SwitchToAsync(normalizedModel, reasoningEffort, cancellationToken);

SDK v0.2.2 on NuGet only has the 4-arg overload — the 3-arg was removed in the v0.2.1→v0.2.2 upgrade. This PR compiles against a local SDK build (likely 0.3.0-local from PureWeen/copilot-sdk) that still has the old 3-arg signature.

Impact: Anyone building from the published NuGet package (v0.2.2) will get a compile error: CS1501: No overload for method 'SwitchToAsync' takes 3 arguments.

Recommendation: This is fine if the intent is to track the local SDK build temporarily. If so, consider adding a comment noting the SDK version dependency. If this should work with both, use #if conditional compilation or keep the 4-arg call.

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Recommended Action

✅ Approve (conditional)

The change is correct for the local SDK build. The risk is limited since the use-local-sdk.sh script and local nuget source would need to be configured for this to compile anyway. Approve with the understanding this is a temporary local-SDK-tracking change.

[PureWeen]

Good catch — this is intentionally tracking the local SDK build which reverted to the 3-arg signature. The Directory.Build.props.local override is active, so the published v0.2.2 NuGet package is not used. When we move back to a published SDK version, this call will need to be updated to match that version's signature.

[PureWeen]

Closing — the v0.3 SDK type renames (McpStdioServerConfig, SystemNotificationXxx, etc.) break compatibility with the published v0.2.2 NuGet package. The code on main already builds clean against v0.2.2. We'll update when v0.3 is published.