eBPF helpers do not fully initialize buffers

@Alan-Jowett is already working on this.

Since Jun 15, 2026.

### Describe the bug

The PREVAIL verifier allows valid BPF code to access uninitialized stack memory in some edge cases.

Specifically, code that uses helper functions which take a pointer argument to a buffer and do not explicitly initialize the buffer on every code path cause the verifier to accept programs that are not valid.

A change in the documentation there will clarify the contract and mention that helpers need to initialize the full buffer range (see https://github.com/vbpf/prevail/pull/1146).

https://github.com/microsoft/ebpf-for-windows/blob/00053ce6b11b51186861b27853a20c6e1927b5fa/libs/execution_context/ebpf_core.c#L2657-L2708 contains functions that return early without initializing the buffer, thus triggering this exact problem.

These functions should explicitly initialize the buffers they operate on to avoid this issue.

### OS information

_No response_

### Steps taken to reproduce bug

Run any of the helper functions that have an early-return path without initializing the buffers they are supposed to operate on.
The verifier will flag such programs as correct.

### Expected behavior

Initialization should be guaranteed to avoid reading from uninitialized memory after calls to helper functions.

### Actual outcome

The verifier accepts the program and uninitialized memory reads are possible.

### Additional details

_No response_