feat(#2220): add low and max effort levels

claude --effort now accepts low, medium, high, xhigh, max.
Expand EFFORT_LEVELS from 3 to 5, update NixOS enum + description,
and fix the stale doc comment in web_ui.rs.

Closes #2220

hive-ag3nt/src/events.rs

@@ -583,7 +583,7 @@ pub const DEFAULT_EFFORT: &str = "medium";
 
 /// Valid claude `--effort` levels, ascending. The operator picker is
 /// constrained to these; [`is_valid_effort`] guards the persist path.
-pub const EFFORT_LEVELS: [&str; 3] = ["medium", "high", "xhigh"];
+pub const EFFORT_LEVELS: [&str; 5] = ["low", "medium", "high", "xhigh", "max"];
 
 /// True iff `level` is one of [`EFFORT_LEVELS`].
 #[must_use]

hive-ag3nt/src/web_ui.rs

@@ -461,7 +461,7 @@ struct StateSnapshot {
     /// runtime via `POST /api/effort`; applies on the next session.
     effort: String,
     /// Selectable effort levels for the picker, ascending. Fixed set
-    /// (`medium`, `high`, `xhigh`) — sourced from
+    /// (`low`, `medium`, `high`, `xhigh`, `max`) — sourced from
     /// [`crate::events::EFFORT_LEVELS`], not operator-configurable like
     /// `available_models`. The frontend renders one button per entry.
     available_efforts: Vec<String>,