cleanup: remove dead IntegrationTests.cs, fix FG02 timing

Deleted IntegrationTests.cs — all 9 tests were Skip placeholders with
empty bodies (await Task.CompletedTask). Increased FG02_RevokeFeeAllowance
delays from 8s to 12s to prevent sequence mismatch on chain propagation.
Result: 816 passed, 0 failed, 0 skipped.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Sentinel-Bluebuilder

tests/Sentinel.SDK.Tests/ExhaustiveChainTests.cs

@@ -333,7 +333,7 @@ public async Task FG02_RevokeFeeAllowance()
         using var user = SentinelWallet.Generate();
         var grantMsg = MessageBuilder.GrantFeeAllowance(_opWallet!.Address, user.Address, 1_000_000);
         await _tx.BroadcastAsync(grantMsg);
-        await Task.Delay(8000);
+        await Task.Delay(12000);
 
         // Revoke
         var revokeMsg = MessageBuilder.RevokeFeeAllowance(_opWallet.Address, user.Address);
@@ -342,7 +342,7 @@ public async Task FG02_RevokeFeeAllowance()
         Assert.True(r.Success, r.RawLog);
 
         // Verify revoked
-        await Task.Delay(8000);
+        await Task.Delay(12000);
         var grants = await _chain!.QueryFeeGrantsAsync(user.Address);
         _out.WriteLine($"Grants after revoke: {grants.Count}");
         Assert.Equal(0, grants.Count);