perf: dump-then-scan JSON serialization for socket payloads (companion to #6116)

[FarhanAliRaza]

Draft companion to #6116 (try-orjson), branched from its head (7f89aed).

Commit 1 adds test_process_event_wire: a benchmark of the full receive -> process -> serialize round trip (event JSON decoded via orjson_loads, processed through BaseStateEventProcessor, delta serialized via orjson_dumps_socket as socket.io's encoder invokes it), parametrized with 5-row and 500-row table deltas. No existing benchmark exercised the serialization path #6116 changes.

Commit 2 (pushed after commit 1's CodSpeed run completes, so the delta is measurable run-over-run) reworks the serialization strategy to dump-then-scan on both backends plus assorted fixes; details in the commit message.

Local walltime medians for the large-delta wire benchmark: 5.01ms before, 3.84ms after (-23%). This PR exists to confirm that delta under CodSpeed instrumentation; findings will be folded back into #6116.

[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
🆕 2 new benchmarks
⏩ 8 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
🆕	Simulation	test_process_event_wire[large_delta]	N/A	31.9 ms	N/A
🆕	Simulation	test_process_event_wire[small_delta]	N/A	3.6 ms	N/A

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_{Comparing FarhanAliRaza:orjson-serialization-fixes (ba68dff) with main (cce9772)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[greptile-apps]

Greptile Summary

This PR introduces optional orjson-backed JSON handling and optimizes websocket payload serialization.

• Adds dump-then-scan serialization with sentinel-based preservation of non-finite floats and colliding strings.
• Wires the new JSON helpers into Socket.IO events, uploads, generated frontend files, and persisted JSON utilities.
• Adds serialization regression coverage and end-to-end event-processing benchmarks.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains within the scope of the displayed follow-up threads.

Important Files Changed

Filename	Overview
packages/reflex-base/src/reflex_base/utils/format.py	Adds optional orjson loading/dumping and socket-specific serialization that preserves non-finite floats through frontend-compatible sentinels.
packages/reflex-base/src/reflex_base/.templates/web/utils/state.js	Adds conditional sentinel revival and fallback rewriting for non-standard bare non-finite tokens.
packages/reflex-base/src/reflex_base/.templates/web/utils/helpers/upload.js	Replaces JSON5 upload-stream parsing with the shared non-finite-aware JSON parser and fallback rewriter.
reflex/app.py	Configures Socket.IO and event processing to use the new optional orjson-backed helpers.
packages/reflex-components-core/src/reflex_components_core/core/_upload.py	Uses the new helpers for upload event arguments and streamed state-update serialization.
tests/units/utils/test_format_orjson.py	Adds focused coverage for backend selection, custom serialization, non-finite values, sentinel collisions, and fallback behavior.
tests/benchmarks/test_event_processing.py	Extends benchmarks to cover complete event decoding, processing, and wire serialization for small and large deltas.
pyproject.toml	Adds orjson as an optional project extra and development dependency.

_{Reviews (2): Last reviewed commit: "perf: dump-then-scan JSON serialization ..." | Re-trigger Greptile}