Speed up progressive snapshots and add completion events

[roodboi]

Summary

• eliminate the normal iterate-path UTF-8 JSON round trip and batch parser hot paths
• add completion events, explicit snapshot policies, deterministic benchmarks, and complex nested coverage
• add OpenAI Agents, Vercel AI SDK, and Mastra integrations plus a real WebSocket browser example
• document the server-side parsing and browser transport tradeoffs with an adversarial SSE, Fetch streams, and WebSocket comparison

Performance

Representative retained benchmark results show a 7.80x gain on Bun and a 36.83x gain on Node for the long-string, one-character-chunk hotspot. Object-heavy cases remain near parity or show modest gains, so this change deliberately stays in TypeScript instead of adding a native addon.

Run bun run benchmark for the formatted comparison table and bun run benchmark --json for machine-readable evidence.

Integration and UX

• deterministic Fixture mode and real OpenAI mode
• server-side partial parsing with complete JSON snapshots per WebSocket message
• incremental dashboard materialization, completion-event log, and a progressive raw JSON panel
• documented conditional decisions from key/value completion events
• runnable examples for core streams, OpenAI Agents, Vercel AI SDK, Mastra, and Bun WebSockets

Verification

• bun run check
• 66 tests passed, 4 opt-in live tests skipped, 2,569 assertions
• packed Node/Bun ESM/CJS and Zod 3, Zod 4, and Zod Mini consumer matrix
• bun run test:coverage (90.84% line coverage)
• bun run examples
• bun run benchmark
• bun run benchmark --completion-scaling
• live OpenAI Agents and Mastra end-to-end runs
• bun audit --production --audit-level=high
• desktop and mobile browser verification of the WebSocket example

[roodboi]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Already looking forward to the next diff.

Reviewed commit: 06e422c493

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