fix(breaker): ignore unhandled exceptions

[thomhurst]

Summary

• record only handled failures and genuine successful outcomes in circuit-breaker state
• leave consecutive and ratio history unchanged for unhandled exceptions
• release half-open probe admission without closing the circuit when a probe throws an unhandled exception
• cover normal async, sync, configured-async, ratio, half-open, and deterministic model transitions
• document that exceptions outside the handling clause do not move breaker state

Validation

• dotnet build Kevlar.slnx -c Release
• dotnet run --project tests/Kevlar.Tests -c Release --no-build -- --timeout 5m (849 passed)
• dotnet run --project tests/Kevlar.IntegrationTests -c Release --no-build -- --timeout 5m (131 passed)
• deterministic model sweep filter (5 passed)
• pwsh scripts/Verify-Docs.ps1
• pwsh scripts/Verify-DocSnippets.ps1 -PackagesPath artifacts/package/release -Version 0.0.0-docs187 (118 snippets; behavior passed)
• npm ci --prefix docs
• npm run build --prefix docs

Benchmarks

CircuitBreakerBenchmarks on .NET 10, closed success path:

Path	Before	After	Allocation
ratio breaker	124.7 ns	123.1 ns	0 B → 0 B
async callback configured	145.3 ns	144.3 ns	0 B → 0 B

Depends on #258, whose repair commits are included in this branch.

Closes #187

[coderabbitai]

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Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 9a946e5f-4f87-4280-882a-f518a46bdcfc

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