[n-lark]

Description

Covers problems 1 and 3 of #2322; problem 2 (flow writes) follows in a separate PR.

Every chart point was a proxy, so filters read points through proxies and every 60th trim re-cloned the series. Now points are stored plain and wrapped only when read, as Vue 3 does, and trims are exact on every message without cloning. Other values are unchanged.

µs, 4 lines	main	Before	After
Time window, 1,000/line	46	230	45
Time window, 5,000/line	127	1,567	229
Point limit, 5,000/line	1,308	1,141	449
Both limits, 5,000/line	1,477	2,060	665
Page load, 5,000/line	11,637	29,891	12,639

Contract changes

• A stored message's _datapoint is the same object as the chart's point, not the same proxy. Writes are still reported; match points by value, not ===.
• filter / keepLatestPerTopic callbacks get plain points, so changing them isn't reported (as on main). No third-party widget calls filter.

Test plan

• Harness also checks each chart's value matches its messages' points
• Breaking each part of the change fails a spec (14 checks)
• Benchmarks against main
• Live Node-RED against main: same page-load data and reload for point-limit, time-window and categorical charts, text and gauge
• Flow reads and writes through function and change nodes, exact limits and windows

Related Issue(s)

Part of #2322

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production
• Link to Changelog Entry PR, or note why one is not needed.

Labels

• Includes a DB migration? -> add the area:migration label