Add autoCompact: false setting to fully disable auto-compaction

Problem

There is no way to fully disable auto-compaction. The only available setting is autoCompactWindow (min 100000, max 1000000), which controls when compaction triggers but not whether it triggers.

For users on Claude Max with 1M context models (Opus 4.6 1M), auto-compaction silently wipes conversation history mid-session. The user loses all visible context with no warning and no way to prevent it.

Current behavior

• autoCompactWindow: 1000000 is the max value, but compaction still triggers
• claude config set --global autoCompact false fails (unknown option)
• No autoCompact boolean exists in the settings.json schema

Expected behavior

A boolean setting like autoCompact: false in settings.json that completely disables automatic compaction, letting users manage context manually with /compact when they choose.

Why this matters

Users with heavy configurations (multiple plugins, MCP servers, hooks, extensive CLAUDE.md) consume significant context before typing anything. This causes auto-compact to trigger earlier than expected, destroying conversation flow. Users should be able to opt out entirely and manage compaction manually.

Environment

• Claude Code v2.1.89
• Model: Opus 4.6 (1M context)
• Platform: macOS (Darwin 25.3.0)
• Plan: Claude Max