## Summary
Fixes a panic that occurred when parsing malformed integrity data in
lockfiles. The issue was in `integrity.zig` where base64 decoding
attempted to write more bytes than the fixed-size digest buffer could
hold, causing `panic: index out of bounds: index 64, len 64`.
## Root Cause
The `Integrity.parse()` function tried to decode base64 data into a
fixed 64-byte buffer without validating that the decoded size wouldn't
exceed the buffer capacity. When malformed or oversized base64 integrity
strings were encountered in lockfiles, this caused an out-of-bounds
write.
## Fix
Added proper bounds checking in `src/install/integrity.zig`:
- Validates expected digest length before decoding
- Checks decoded size against buffer capacity using `calcSizeForSlice()`
- Only decodes into appropriately sized buffer slice based on hash
algorithm
- Returns `unknown` tag for malformed data instead of panicking
## Test Plan
- [x] Verified release binary crashes with malformed integrity data
- [x] Verified debug build with fix handles malformed data gracefully
- [x] Added comprehensive regression tests for all hash types (sha1,
sha256, sha384, sha512)
- [x] Confirmed normal lockfile parsing continues to work correctly
- [x] Tests pass: `bun bd test
test/regression/issue/integrity-base64-bounds-check.test.ts`
## Before/After
**Before**: `panic: index out of bounds: index 64, len 64`
**After**: Graceful handling with warning about malformed integrity data
🤖 Generated with [Claude Code](https://claude.ai/code)
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
