fix: skip provider sessions during SDK reconnect

[Redth]

Summary

• skip provider and other virtual sessions when recreating the shared Copilot SDK client after a JSON-RPC disconnect
• avoid invalid session.resume calls against synthetic provider session IDs like provider:papilot:leader
• add a regression guard covering the sibling reconnect path

Why

When the Copilot CLI transport dropped, PolyPilot tried to re-resume Papilot provider sessions using their persistence-only IDs. Those are not real CLI session IDs, so reconnect recovery could cascade into more errors and leave provider chats looking broken.

Testing

• /opt/homebrew/bin/dotnet test PolyPilot.Tests/PolyPilot.Tests.csproj --no-restore --filter "ConnectionRecoveryTests"

[PureWeen]

🔍 Multi-Model Code Review — PR #569

PR: fix: skip provider sessions during SDK reconnect
Branch: fix/provider-session-reconnect-recovery → main
Changes: +30 / -0 across 2 files (1 production, 1 test)
CI Status: ⚠️ No CI checks reported on this branch
Prior Reviews: None

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🟢 MINOR — Structural test could also assert guard ordering relative to ForceCompleteProcessingAsync

File: PolyPilot.Tests/ConnectionRecoveryTests.cs:287-290
Flagged by: 1/3 reviewers (production code verified correct by another reviewer)

The test asserts the provider-skip guard appears before ResumeSessionAsync, but not before ForceCompleteProcessingAsync. The production ordering is correct today — the guard is inserted before the IsProcessing check that gates ForceCompleteProcessingAsync. But the test wouldn't catch a future refactor that moves the guard between those two calls.

Suggested improvement:

var forceCompleteIndex = source.IndexOf("ForceCompleteProcessingAsync(kvp.Key", loopIndex, StringComparison.Ordinal);
Assert.True(skipIndex < forceCompleteIndex,
    "Provider-session skip must appear before ForceCompleteProcessingAsync");

Not blocking — this is a test hardening suggestion, not a production bug.

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✅ Verified Correct

• Guard completeness — Session == null catches all non-SDK session types (provider leaders/members, demo/remote/lazy-resume placeholders). IsProviderSession(kvp.Key) is defense-in-depth for any future case where a provider session gets a non-null Session.
• Ordering — guard runs after string.IsNullOrEmpty(SessionId) (provider sessions have non-empty synthetic IDs like "provider:{id}:leader" so they pass that check), and before both the IsProcessing/ForceCompleteProcessingAsync block and ResumeSessionAsync.
• Provider Session is always null — provider sessions are created with Session = null! (Providers.cs:129, 382) and no code path assigns a real CopilotSession afterward.
• Debug logging — correctly logs skipped sessions for diagnostics.
• Test quality — structural regression guard follows established ConnectionRecoveryTests patterns with clear ordering assertions.

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🏁 Recommendation: ✅ Approve

Clean, minimal, well-scoped fix. The guard correctly prevents invalid session.resume calls against synthetic provider session IDs during SDK reconnect recovery.