fix(context): show both summarize and compress thresholds in /context

The /context command previously showed only the hard budget compression
threshold (contextWindow - maxTokens), which confused users who expected
to see the soft summarization trigger from summarize_token_percent.

This commit adds SummarizeAtTokens alongside the existing CompressAtTokens
so that both thresholds are visible:

- Compress at: contextWindow - maxTokens (hard budget, triggers proactive
  compression when exceeded)
- Summarize at: contextWindow * summarizeTokenPercent / 100 (soft trigger,
  matches maybeSummarize's threshold)

The fix updates the /context command output, the Web UI popover, and the
pico channel WebSocket payload.

Fixes #2968

pkg/agent/agent_command.go

@@ -350,11 +350,12 @@ func (al *AgentLoop) buildCommandsRuntime(
 			}
 			history := agent.Sessions.GetHistory(opts.SessionKey)
 			return &commands.ContextStats{
-				UsedTokens:       usage.UsedTokens,
-				TotalTokens:      usage.TotalTokens,
-				CompressAtTokens: usage.CompressAtTokens,
-				UsedPercent:      usage.UsedPercent,
-				MessageCount:     len(history),
+				UsedTokens:        usage.UsedTokens,
+				TotalTokens:       usage.TotalTokens,
+				CompressAtTokens:  usage.CompressAtTokens,
+				SummarizeAtTokens: usage.SummarizeAtTokens,
+				UsedPercent:       usage.UsedPercent,
+				MessageCount:      len(history),
 			}
 		}
 	}

pkg/agent/context_usage.go

@@ -61,6 +61,13 @@ func computeContextUsage(agent *AgentInstance, sessionKey string) *bus.ContextUs
 	// proactive trigger (msgTokens + toolTokens + maxTokens > contextWindow).
 	compressAt := effectiveWindow
 
+	// summarizeAt = soft summarization trigger: matches maybeSummarize's
+	// threshold (contextWindow * SummarizeTokenPercent / 100).
+	summarizeAt := contextWindow * agent.SummarizeTokenPercent / 100
+	if summarizeAt <= 0 {
+		summarizeAt = compressAt
+	}
+
 	usedPercent := 0
 	if compressAt > 0 {
 		usedPercent = usedTokens * 100 / compressAt
@@ -70,9 +77,10 @@ func computeContextUsage(agent *AgentInstance, sessionKey string) *bus.ContextUs
 	}
 
 	return &bus.ContextUsage{
-		UsedTokens:       usedTokens,
-		TotalTokens:      contextWindow,
-		CompressAtTokens: compressAt,
-		UsedPercent:      usedPercent,
+		UsedTokens:        usedTokens,
+		TotalTokens:       contextWindow,
+		CompressAtTokens:  compressAt,
+		SummarizeAtTokens: summarizeAt,
+		UsedPercent:       usedPercent,
 	}
 }