perf: Optimize hotpath memory management and reduce allocations
- Replace hex::encode(to_be_bytes()) with direct format!("{:016x}") in
TurboHash::hash(), eliminating intermediate byte array and the hex
crate dependency entirely
- Pre-size capnp first segment for FileHashes, LockFilePackages, and
LockFilePackagesRef based on entry count, avoiding repeated segment
growth allocations during message construction
- Use as_str() instead of to_string() for package_dir in TaskHashable
serialization, avoiding a per-task-hash String allocation
- Replace HashSet with sort_unstable+dedup in calculate_dependency_hashes,
removing HashSet hashing overhead and reducing allocations when
dependency fan-out is large
- Pre-allocate HashMap capacity in RepoGitIndex::get_package_hashes
using exact count (full-repo) or BTreeMap range size_hint (per-package)
- Use String::new() instead of "".into() for zero-allocation empty
string returns in get_external_deps_hash and get_internal_deps_hash
https://claude.ai/code/session_01TXs2FAMUjxXr25hLQwTMzF
