fix: preserve URL query strings in invoke output (#54)

## Summary
- Fixes pretty-printed `kernel invoke` output escaping `&` as `\\u0026`
(and similarly `<`, `>`), which breaks copy/paste of URLs returned in
invocation output (e.g. replay URLs).
- Switches JSON pretty-printing to a custom encoder with
`SetEscapeHTML(false)`.

## Why
Go's default `json.MarshalIndent` escapes HTML-sensitive characters.
When the CLI re-marshals invocation output for pretty printing, URLs
like `...?jwt=...&replay_id=...` can show up as
`...?jwt=...\\u0026replay_id=...`.

## Test plan
- `go test ./...`

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Prevents HTML character escaping in pretty-printed invoke results by
using a custom JSON encoder to preserve URL characters.
> 
> - **CLI – `cmd/invoke.go`**:
> - Use custom JSON encoder for `printResult` with
`SetEscapeHTML(false)` and indentation to avoid escaping `&`, `<`, `>`
in pretty-printed output; trims trailing newline.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
f3502a4. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: dprevoznik

cmd/invoke.go

@@ -1,6 +1,7 @@
 package cmd
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"fmt"
@@ -194,8 +195,15 @@ func handleSdkError(err error) error {
 func printResult(success bool, output string) {
 	var prettyJSON map[string]interface{}
 	if err := json.Unmarshal([]byte(output), &prettyJSON); err == nil {
-		bs, _ := json.MarshalIndent(prettyJSON, "", "  ")
-		output = string(bs)
+		// Use a custom encoder to prevent escaping &, <, > as \u0026, \u003c, \u003e
+		// which breaks copy/paste of URLs in the invoke output.
+		var buf bytes.Buffer
+		encoder := json.NewEncoder(&buf)
+		encoder.SetEscapeHTML(false)
+		encoder.SetIndent("", "  ")
+		if err := encoder.Encode(prettyJSON); err == nil {
+			output = strings.TrimSuffix(buf.String(), "\n")
+		}
 	}
 	// use pterm.Success if succeeded, pterm.Error if failed
 	if success {