docs(fix[pane/respawn-pane]): switch JSON ellipsis block to json5

The PaneInfo response example used a bare `...` inside a ```json fence to
indicate truncated fields. Pygments' strict JSON lexer errored at the `.`
token and fell back to relaxed mode, surfacing
`WARNING: Lexing literal_block ... as "json" resulted in an error at
token: '.'.` on every Sphinx build.

Switching the fence to json5 (Pygments ships a json5 lexer; jsonc is not
registered) and rewriting `...` as `// ...` keeps the same visual intent
while staying within the lexer's accepted grammar — the line now
highlights as a comment instead of triggering a lex error.

Author: tony

docs/tools/pane/respawn-pane.md

@@ -69,13 +69,13 @@ The audit log redacts each `environment` *value* via `{len, sha256_prefix}` dige
 
 Response (PaneInfo):
 
-```json
+```json5
 {
   "pane_id": "%5",
   "pane_pid": "98765",
   "pane_current_command": "pytest",
   "pane_current_path": "/home/user/project",
-  ...
+  // ...
 }
 ```