Fix performance attention runtime interop

[Gujiassh]

Summary

• adapt the performance package to the CommonJS class exports that @ruvector/attention actually ships instead of the stale type surface exposed by its declarations
• route benchmark and quick-test code through the local compatibility layer so the package, examples, and tests all agree on one runtime-safe import path
• keep the change isolated to @claude-flow/performance, separate from the open PluginManager and benchmark-environment PR lines

Validation

• cd v3 && npx vitest run @claude-flow/performance/tests/attention.test.ts @claude-flow/performance/tests/benchmarks.test.ts
• cd v3/@claude-flow/performance && npm run build
• lsp_diagnostics clean on attention-integration.ts, attention-benchmarks.ts, and examples/quick-test.ts

Notes

• the installed @ruvector/attention package still ships root typings that do not describe its real runtime exports; this PR fixes the performance package without modifying the external dependency itself