[Windows] Implement AutoStart: add examples and fix C API array cleanup

[Copilot]

Adds working examples for the AutoStart API (C++ and C) and fixes a C API memory management issue where callers were incorrectly instructed to use delete[] directly — which is not valid from C code.

C API fix

• Added native_autostart_free_arguments() to autostart_c.h/autostart_c.cpp for proper C-compatible cleanup of argument arrays returned by native_autostart_get_arguments()

Examples

• examples/autostart_example/ — C++ example covering Enable, Disable, IsEnabled, SetProgram, and default-detection behavior
• examples/autostart_c_example/ — C equivalent using the native_autostart_* C API
• Both added to root CMakeLists.txt

// Before (documented but broken for C consumers):
char** args; size_t n;
native_autostart_get_arguments(as, &args, &n);
delete[] args;  // ❌ not valid C

// After:
native_autostart_get_arguments(as, &args, &n);
native_autostart_free_arguments(args, n);  // ✅ works from C and C++

Platform notes for the underlying Windows implementation: uses HKCU\Software\Microsoft\Windows\CurrentVersion\Run with no elevated privileges required.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[Windows] Implement AutoStart</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Windows] Implement AutoStart #32

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