fix(data-warehouse): improve SQL editor typing latency

[lordspline]

Problem

Large SQL editor documents could make typing feel frozen because active-query decorations synchronously re-parsed the current SQL document after every content change. This addresses PostHog#60974.

Changes

• Coalesce active-query decoration refreshes behind the existing short scheduling path used for cursor-driven decoration updates.
• Keep query input, draft state, URL state, save/run behavior, and metadata parsing independent from the visual decoration schedule.
• Add a deterministic large-SQL benchmark plus focused unit coverage for the decoration scheduling behavior.

How did you test this code?

• Agent-run benchmark: SQL_EDITOR_LATENCY_BENCHMARK=1 hogli test frontend/src/scenes/data-warehouse/editor/sqlEditorLatency.benchmark.test.ts
  • 32,855-byte generated SQL document on 16 vCPU AMD EPYC 9254 / 31 GiB VM
  • Before: input-ready median 596.2 ms, p95 699.8 ms across 5 benchmark runs
  • After: input-ready median 1.7 ms, p95 2.8 ms across 5 benchmark runs
• Agent-run tests: hogli test frontend/src/scenes/data-warehouse/editor/sqlEditorLogic.test.ts frontend/src/scenes/data-warehouse/editor/multiQueryUtils.test.ts
• Agent-run formatting: pnpm --filter=@posthog/frontend format
• Agent-run typecheck: pnpm --filter=@posthog/frontend typescript:check
• Agent browser verification covered normal and large-query typing, paste, undo/redo, tab switching, running, and saving.

Automatic notifications

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

Docs update

No docs update needed; this is a SQL editor interaction-performance fix.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Capy reproduced the issue with a deterministic large SQL document and profiled before changing code. The dominant hot path was HogQL parser/WASM work from active-query decoration refreshes, so the fix moves only that visual decoration work off the keypress-ready path instead of debouncing the editor state itself.

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