KNT-0026: prototype component-scoped partial row rendering

[IRus]

Context

KNT-0026 is the component-scoped re-rendering idea: today a browser event dispatch invalidates the runtime and BrowserKineticaApp immediately performs a full root render. Memoized keyed each rows already know which cells they read, so the prototype tests whether a cell write can re-render only the affected keyed row and patch that mounted DOM subtree.

Prototype branch: https://github.com/Heapy/kinetica/tree/agent/knt-0026-partial-row-render
Commit: ef19383

This branch was created from latest origin/main at 9238046 and carries the prototype from the local knt-0026-prototype worktree.

Prototype shape

• Registers partial render targets for memoized keyed each rows that emit exactly one keyed node.
• Tracks target dependencies as ObservableCell -> partial target ids in KineticaRuntime.
• On StateCellImpl writes, marks only dependent targets dirty when possible.
• Browser production path consumes a partial render batch after event dispatch and patches matching mounted keyed nodes.
• Falls back to full render for manual/global invalidation, missing targets, non-partial dependencies, debug mode, and unsafe patch targets.

Benchmark notes

10k benchmark, median:

operation	baseline	prototype	delta
select10k	10.28 ms	7.37 ms	-28.3%
create10k	291.79 ms	297.78 ms	+2.1%
clear1k	6.66 ms	6.94 ms	+4.2%
remove10k	68.31 ms	69.01 ms	+1.0%
update10th10k	43.07 ms	46.45 ms	+7.8%

100k direct select harness, median, 1 warmup + 5 samples:

operation	baseline	prototype	delta
select100k direct	179.94 ms	66.67 ms	-62.9%

100k direct update smoke, single sample:

operation	baseline	prototype	delta
update100k direct	686.88 ms	657.63 ms	-4.3%

The 100k direct harness builds 100k rows once and clicks a row through DOM child indexing to avoid Playwright selector overhead. It still exercises the real browser event path and render/patch/paint path, but it is not the exact official scaling driver.

Validation

• ./kotlin task :kinetica-compiler:publishToMavenLocal
• ./kotlin task :kinetica-browser:linkJsTest
• ./kotlin task :kinetica-runtime:testJvm (208/208 tests passed)

Known gaps

• Not PR-ready: this is a measurement prototype.
• Partial browser path is disabled in debug mode.
• currentTree / tree() can remain stale after a partial browser patch.
• Mounted lookup is keyed-only, so key collisions across independent regions are not handled robustly.
• Partial targets are limited to memoized keyed each rows with one keyed emitted node.
• Registry maintenance adds overhead on create/update paths; the benefit is currently concentrated in row-local cell writes.

Next steps

• Replace global keyed lookup with a frame/region-scoped mounted identity.
• Decide how partial renders update the retained logical tree or make tree() semantics explicit.
• Add browser tests for partial success and fallback behavior.
• Add an official benchmark mode for 100k direct row interactions so this can be repeated without ad hoc harness code.