fix(Cause): align toJSON key with actual property name

[lihan3238]

Closes #4683

Summary

The Fail case in Cause.toJSON used the key "failure" but the actual property name is "error". All other variants (Die, Interrupt, Sequential, Parallel) already use keys matching their property names.

This inconsistency means:

• console.log(cause) shows { _tag: "Fail", failure: ... }
• But accessing cause.failure is undefined — the actual property is cause.error

Fix

Changed the toJSON key from "failure" to "error" in the Fail case to match the actual property name.

Test Plan

• Updated existing toJSON test expectations in Cause.test.ts
• All 72 Cause tests pass

[changeset-bot]

🦋 Changeset detected

Latest commit: 8771e8e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 36 packages

Name	Type
effect	Patch
@effect/cli	Patch
@effect/cluster	Patch
@effect/experimental	Patch
@effect/opentelemetry	Patch
@effect/platform-browser	Patch
@effect/platform-bun	Patch
@effect/platform-node-shared	Patch
@effect/platform-node	Patch
@effect/platform	Patch
@effect/printer-ansi	Patch
@effect/printer	Patch
@effect/rpc	Patch
@effect/sql-clickhouse	Patch
@effect/sql-d1	Patch
@effect/sql-drizzle	Patch
@effect/sql-kysely	Patch
@effect/sql-libsql	Patch
@effect/sql-mssql	Patch
@effect/sql-mysql2	Patch
@effect/sql-pg	Patch
@effect/sql-sqlite-bun	Patch
@effect/sql-sqlite-do	Patch
@effect/sql-sqlite-node	Patch
@effect/sql-sqlite-react-native	Patch
@effect/sql-sqlite-wasm	Patch
@effect/sql	Patch
@effect/typeclass	Patch
@effect/vitest	Patch
@effect/workflow	Patch
@effect/ai	Patch
@effect/ai-amazon-bedrock	Patch
@effect/ai-anthropic	Patch
@effect/ai-google	Patch
@effect/ai-openai	Patch
@effect/ai-openrouter	Patch

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