fix(dashboard/memory): bound KV row output - #7494

Substantive changes

• Replace raw per-agent KV query errors with fixed localized UI copy.
• Centralize visible-cell and hover-preview truncation semantics.
• Add focused coverage for error redaction and both preview bounds.

Verification

• mise exec -- pnpm test --run src/pages/Memory/components/AgentKvRows.test.tsx (2 tests passed)
• mise exec -- pnpm typecheck
• mise exec -- pnpm exec eslint src/pages/Memory/components/AgentKvRows.tsx src/pages/Memory/components/AgentKvRows.test.tsx src/pages/Memory/constants.ts
• mise exec -- pnpm lint
• mise exec -- pnpm test --run (102 files, 1077 tests passed)
• mise exec -- pnpm build
• mise exec -- pnpm test:i18n-parity (known baseline only: Polish and Ukrainian each retain the same eight extra plural keys; Korean and Chinese match English)

Out-of-scope follow-ups

• The inaccurate full-tooltip promise in Memory/constants.ts remains pending because open fix: align memory embedding provider catalog #7472 owns that file. Re-audit the preview contract on its post-merge source instead of stacking a conflicting edit.
• Other Memory page audit findings remain separate component-level clusters in the handoff inventory.