Add dashboard block-next-time flow

[knhn1004]

Summary

• add a right-click dashboard event action to open Add Rule with an exact deny preset
• store minimal rule-matching tool context on new ledger entries
• cover preset generation and SSE ledger context with focused tests

Tests

• bun test tests/eventRulePreset.test.ts
• bun run typecheck
• bun run build
• CGO_ENABLED=1 CGO_CFLAGS="-I/Users/oliver/code/OpenAgentLock/ledger/include" CGO_LDFLAGS="-L/Users/oliver/code/OpenAgentLock/ledger/target/x86_64-apple-darwin/release -lopenagentlock_ledger" go test ./internal/api -run 'TestLedgerTail|TestGateCheck'
• git diff --check

Linear: OAL-46