policy, state: correct MatchersForNode's doc

It filters routes. Peers come from BuildPeerMap.

Updates #3626

hscontrol/policy/pm.go

@@ -16,7 +16,7 @@ type PolicyManager interface {
 	Filter() ([]tailcfg.FilterRule, []matcher.Match)
 	// FilterForNode returns filter rules for a specific node, handling autogroup:self
 	FilterForNode(node types.NodeView) ([]tailcfg.FilterRule, error)
-	// MatchersForNode returns matchers for peer relationship determination (unreduced)
+	// MatchersForNode returns the unreduced matchers that filter the routes a node sees
 	MatchersForNode(node types.NodeView) ([]matcher.Match, error)
 	// BuildPeerMap constructs peer relationship maps for the given nodes
 	BuildPeerMap(nodes views.Slice[types.NodeView]) map[types.NodeID][]types.NodeID

hscontrol/policy/v2/policy.go

@@ -1052,7 +1052,7 @@ func (pm *PolicyManager) FilterForNode(node types.NodeView) ([]tailcfg.FilterRul
 	return pm.filterForNodeLocked(node), nil
 }
 
-// MatchersForNode returns the matchers for peer relationship determination for a specific node.
+// MatchersForNode returns the matchers that filter the routes a node sees.
 // These are UNREDUCED matchers - they include all rules where the node could be either source or destination.
 // This is different from [PolicyManager.FilterForNode] which returns REDUCED rules for packet filtering.
 //
@@ -1060,8 +1060,7 @@ func (pm *PolicyManager) FilterForNode(node types.NodeView) ([]tailcfg.FilterRul
 // For autogroup:self: returns node-specific matchers from unreduced compiled rules.
 //
 // Per-node results are cached and invalidated on policy/node updates
-// so [PolicyManager.BuildPeerMap]'s O(N²) slow path avoids recomputing
-// matchers for every pair.
+// so building a node's map does not recompile them.
 func (pm *PolicyManager) MatchersForNode(node types.NodeView) ([]matcher.Match, error) {
 	if pm == nil {
 		return nil, nil

hscontrol/state/state.go

@@ -1683,7 +1683,7 @@ func (s *State) FilterForNode(node types.NodeView) ([]tailcfg.FilterRule, error)
 	return s.polMan.FilterForNode(node)
 }
 
-// MatchersForNode returns matchers for peer relationship determination (unreduced).
+// MatchersForNode returns the unreduced matchers that filter the routes a node sees.
 func (s *State) MatchersForNode(node types.NodeView) ([]matcher.Match, error) {
 	return s.polMan.MatchersForNode(node)
 }