docs(tools): Show is_caller=false as the default example value

why: is_caller is null only when the MCP client runs outside tmux
(no TMUX_PANE env var). An MCP agent running inside a tmux pane —
the overwhelmingly common case — gets true or false depending on
whether the targeted pane matches its own. Seeding every result
example with `"is_caller": null` misrepresents the typical shape
of a response and trains readers to expect an edge-case value.

what:
- docs/tools/panes.md: all 9 occurrences changed from `"is_caller":
  null` to `"is_caller": false` (example tool calls target panes
  like %0 that are not the implicit caller, so false is the
  realistic value).
- docs/tools/windows.md: 3 occurrences changed likewise.

The is_caller Pydantic field definition in models.py still allows
None for the outside-tmux case — schema unchanged.

Author: tony

docs/tools/panes.md

@@ -81,7 +81,7 @@ Response:
   "pane_active": "1",
   "window_id": "@0",
   "session_id": "$0",
-  "is_caller": null
+  "is_caller": false
 }
 ```
 
@@ -130,7 +130,7 @@ Response:
       "FAIL: test_upload (AssertionError)",
       "3 tests: 2 passed, 1 failed"
     ],
-    "is_caller": null
+    "is_caller": false
   }
 ]
 ```
@@ -226,7 +226,7 @@ Response:
   "title": null,
   "pane_current_command": "zsh",
   "pane_current_path": "/home/user/myproject",
-  "is_caller": null
+  "is_caller": false
 }
 ```
 
@@ -381,7 +381,7 @@ Response:
   "pane_active": "1",
   "window_id": "@0",
   "session_id": "$0",
-  "is_caller": null
+  "is_caller": false
 }
 ```
 
@@ -453,7 +453,7 @@ Response:
   "pane_active": "1",
   "window_id": "@0",
   "session_id": "$0",
-  "is_caller": null
+  "is_caller": false
 }
 ```
 
@@ -498,7 +498,7 @@ Response:
   "pane_active": "1",
   "window_id": "@0",
   "session_id": "$0",
-  "is_caller": null
+  "is_caller": false
 }
 ```
 
@@ -542,7 +542,7 @@ Response:
   "pane_active": "1",
   "window_id": "@0",
   "session_id": "$0",
-  "is_caller": null
+  "is_caller": false
 }
 ```
 
@@ -643,7 +643,7 @@ Response:
   "pane_active": "1",
   "window_id": "@0",
   "session_id": "$0",
-  "is_caller": null
+  "is_caller": false
 }
 ```
 
@@ -686,7 +686,7 @@ Response:
   "pane_active": "1",
   "window_id": "@0",
   "session_id": "$0",
-  "is_caller": null
+  "is_caller": false
 }
 ```
 

docs/tools/windows.md

@@ -94,7 +94,7 @@ Response:
     "pane_active": "1",
     "window_id": "@0",
     "session_id": "$0",
-    "is_caller": null
+    "is_caller": false
   },
   {
     "pane_id": "%1",
@@ -108,7 +108,7 @@ Response:
     "pane_active": "0",
     "window_id": "@0",
     "session_id": "$0",
-    "is_caller": null
+    "is_caller": false
   }
 ]
 ```
@@ -194,7 +194,7 @@ Response:
   "pane_active": "0",
   "window_id": "@0",
   "session_id": "$0",
-  "is_caller": null
+  "is_caller": false
 }
 ```