effortLevel setting doesn't support "max" value

Bug

/effort max works as a session-only command and sets effort to "Maximum capability with deepest reasoning (Opus 4.6 only)", but this value cannot be persisted in settings.json.

The effortLevel field in the settings schema only allows "low", "medium", "high":

"effortLevel": {
  "description": "Persisted effort level for supported models.",
  "type": "string",
  "enum": ["low", "medium", "high"]
}

Setting "effortLevel": "max" in ~/.claude/settings.json is silently ignored (falls back to default).

Expected behavior

"max" should be a valid value in the effortLevel enum so it can be persisted across sessions, just like the other effort levels.

Steps to reproduce

1. Run /effort max — works, confirms "Set effort level to max (this session only)"
2. Add "effortLevel": "max" to ~/.claude/settings.json
3. Restart Claude Code
4. Run /effort — shows "high", not "max"

Environment

• Windows 11 Pro
• Claude Code CLI
• Model: Opus 4.6