fix: parallelize memory kv batches

[wbugitlab1]

Summary

• Parallelize independent KV reads/writes in semantic consolidation and decay.
• Batch reflect insight lookups/writes while preserving provider call ordering and duplicate insight semantics.
• Add concurrency and batch-failure regression coverage.

Verification

• corepack pnpm exec vitest run --exclude test/integration.test.ts test/consolidation-pipeline.test.ts test/reflect.test.ts passed: 2 files / 35 tests.
• corepack pnpm run lint passed.
• corepack pnpm run build passed with existing tsdown warnings.
• corepack pnpm test passed: 202 files / 2804 tests.
• semgrep scan --config p/default --error --metrics=off . passed with 0 findings.
• gitleaks protect --staged --redact passed with no leaks.

No schema, API, auth, dependency, provider prompt, MCP/REST surface, or remote-target changes.