feat: Add gt peek command and session communication docs

Adds gt peek as ergonomic alias for gt session capture:
  gt peek gastown/furiosa      # Last 100 lines
  gt peek gastown/furiosa 50   # Last 50 lines

Creates nudge/peek pair as canonical session interface:
  gt nudge - send TO session (reliable delivery)
  gt peek  - read FROM session (capture-pane wrapper)

Adds docs/session-communication.md explaining:
- Why raw tmux send-keys is unreliable for Claude
- The reliable NudgeSession pattern (literal + delay + Enter)
- Command reference and common patterns
- Guidance for template authors

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/peek.go

@@ -0,0 +1,68 @@
+package cmd
+
+import (
+	"fmt"
+	"strconv"
+
+	"github.com/spf13/cobra"
+)
+
+// Peek command flags
+var peekLines int
+
+func init() {
+	rootCmd.AddCommand(peekCmd)
+	peekCmd.Flags().IntVarP(&peekLines, "lines", "n", 100, "Number of lines to capture")
+}
+
+var peekCmd = &cobra.Command{
+	Use:   "peek <rig/polecat> [count]",
+	Short: "View recent output from a polecat session",
+	Long: `Capture and display recent terminal output from a polecat session.
+
+This is the ergonomic alias for 'gt session capture'. Use it to check
+what an agent is currently doing or has recently output.
+
+The nudge/peek pair provides the canonical interface for agent sessions:
+  gt nudge - send messages TO a session (reliable delivery)
+  gt peek  - read output FROM a session (capture-pane wrapper)
+
+Examples:
+  gt peek gastown/furiosa         # Last 100 lines (default)
+  gt peek gastown/furiosa 50      # Last 50 lines
+  gt peek gastown/furiosa -n 200  # Last 200 lines`,
+	Args: cobra.RangeArgs(1, 2),
+	RunE: runPeek,
+}
+
+func runPeek(cmd *cobra.Command, args []string) error {
+	address := args[0]
+
+	// Handle optional positional count argument
+	lines := peekLines
+	if len(args) > 1 {
+		n, err := strconv.Atoi(args[1])
+		if err != nil {
+			return fmt.Errorf("invalid line count: %s", args[1])
+		}
+		lines = n
+	}
+
+	rigName, polecatName, err := parseAddress(address)
+	if err != nil {
+		return err
+	}
+
+	mgr, _, err := getSessionManager(rigName)
+	if err != nil {
+		return err
+	}
+
+	output, err := mgr.Capture(polecatName, lines)
+	if err != nil {
+		return fmt.Errorf("capturing output: %w", err)
+	}
+
+	fmt.Print(output)
+	return nil
+}