fix(sql-editor): debounce decoration updates while typing

[xPolar]

Problem

Editing large SQL queries stalls the editor because every input update resolves the active subquery immediately. That path parses the full query with the HogQL WASM parser before the browser can paint.

Fixes PostHog#60974.

Changes

• Debounce active-query decoration work until typing or cursor movement has been idle for 150 ms.
• Use the keyed Kea disposable for replacement and unmount cleanup.
• Add a regression test proving rapid query updates produce one deferred decoration update.

How did you test this code?

• Ran all 63 tests in sqlEditorLogic.test.ts.
• Ran the frontend TypeScript check and formatting check.
• Benchmarked 24 edits at a 50 ms key interval in Chromium against the same 16,576-byte, 250-CTE query. Keydown-to-next-paint latency fell from 391.7 ms median / 441.1 ms p95 to 21.2 ms median / 26.7 ms p95. CDP sampling attributed the baseline long tasks to the HogQL WASM parser; the final browser run retained all typed text and reduced parser long tasks from one per edit to one after the debounce settled.

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

Docs update

No documentation changes are needed for this editor performance fix.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Captain Capy reproduced and profiled the issue with a Playwright/Chrome DevTools benchmark. The chosen fix defers existing decoration work rather than caching parser output globally, keeping behavior scoped to each editor logic while eliminating per-keystroke parsing.

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