GHSA-x494-mj8g-cj27

### Summary Multiple denial-of-service vectors in `gix-pack`: unchecked array indexing causes panics on crafted delta data, and uncapped attacker-controlled size headers enable OOM process kills. Both are triggered by malicious pack data received during clone/fetch. ### Details **Bug 1: Unchecked array indexing in delta application (CWE-248)** The `apply()` function in `gix-pack/src/data/delta.rs` (lines 33-87) reads delta instructions using unchecked `data[i]` indexing at 7 locations (lines 41, 45, 49, 53, 57, 61, 65). The command byte's bits indicate how many additional bytes follow, but if the delta data is truncated, the index panics: ```rust pub(crate) fn apply(base: &[u8], mut target: &mut [u8], data: &[u8]) -> Result<(), apply::Error> { let mut i = 0; while let Some(cmd) = data.get(i) { // first byte: safely checked i += 1; match cmd { cmd if cmd & 0b1000_0000 != 0 => { let (mut ofs, mut size): (u32, u32) = (0, 0); if cmd & 0b0000_0001 != 0 { ofs = u32::from(data[i]); // PANIC: no bounds check i += 1; } // ... 6 more unchecked data[i] at lines 45, 49, 53, 57, 61, 65 ``` Lines 83-84 use `assert_eq!` (not `debug_assert_eq!`) that panics in both debug and release builds: ```rust assert_eq!(i, data.len()); assert_eq!(target.len(), 0); ``` A second location in `parse_header_info()` (`gix-pack/src/data/entry/decode.rs:116-129`) also panics on truncated input via unchecked `data[0]` and `data[i]`. Note: PR #2059 (merged 2025-06-25) fixed the explicit `panic!()` for command code 0. The unchecked array indexing is a distinct class that remains unfixed. **Bug 2: Uncapped allocation from attacker-controlled size headers (CWE-770)** Pack entry headers and delta headers encode object sizes as LEB128-encoded u64 values. These sizes are used to allocate buffers before validating the actual data, with no upper bou