[scheduler] Address Copilot feedback: %p type, NameType doc, test docstring

- Strip const for the %p varargs call (the format spec takes void*, not
  const void*; same representation everywhere but pedantically correct).
- Mention SELF_POINTER in the NameType discriminator comment.
- Update test docstring to match the actual const void * signatures.

esphome/core/scheduler.cpp

@@ -60,8 +60,9 @@ struct SchedulerNameLog {
       return buffer;
     } else {  // SELF_POINTER
       // static_name carries the void* key for SELF_POINTER (pointer-width union slot).
-      // Cast to const void* — %p requires a void* argument.
-      ESPHOME_snprintf_P(buffer, sizeof(buffer), ESPHOME_PSTR("self:%p"), static_cast<const void *>(static_name));
+      // %p is specified as void* (not const void*), so strip const for the varargs call.
+      ESPHOME_snprintf_P(buffer, sizeof(buffer), ESPHOME_PSTR("self:%p"),
+                         const_cast<void *>(static_cast<const void *>(static_name)));
       return buffer;
     }
   }

esphome/core/scheduler.h

@@ -146,7 +146,8 @@ class Scheduler {
   }
 
   // Name storage type discriminator for SchedulerItem
-  // Used to distinguish between static strings, hashed strings, numeric IDs, and internal numeric IDs
+  // Used to distinguish between static strings, hashed strings, numeric IDs, internal numeric IDs,
+  // and self-keyed pointers (caller-supplied `void *`, typically `this`).
   enum class NameType : uint8_t {
     STATIC_STRING = 0,        // const char* pointer to static/flash storage
     HASHED_STRING = 1,        // uint32_t FNV-1a hash of a runtime string