feat(invariant): track handler assertion failures independently during continuous runs

[grandizzy]

Summary

Follow-up to #12587 (assert all invariants on continuous_run). Two improvements to handler assertion tracking during invariant campaigns:

1. Keep running after all invariants are broken

Currently the campaign stops when all invariants break (can_continue returns false). However, there may still be undiscovered assertion failures in handler functions. The campaign should continue running for its full runs/timeout to catch these.

2. Track broken handlers separately

Once a handler assertion fails, record it but stop re-checking its assertions on subsequent calls. The handler should still be called for sequence building (it may trigger interesting state transitions) but its known-broken assertions should be suppressed to avoid noise.

Implementation sketch:

• Add broken_handlers: HashSet<(Address, Selector)> to InvariantTest
• Decouple "record failure" from "stop campaign" in the main fuzz loop
• Track handler assertion failures separately in InvariantFailures (handler_errors map)
• Report handler failures alongside invariant failures in output

Related: #14437, #12587
cc @rappie (original suggestion: #12587 (comment))

[0xalpharush]

See also 0xalpharush@2a96ba3