build: Add clap_complete, libc dependencies and git hash build script

Add clap_complete for shell completion generation and libc (unix-only)
for SIGPIPE handling. Create build.rs to embed the git commit hash at
compile time via cargo:rustc-env=GIT_HASH, enabling `lore version` to
display the short hash alongside the version number.

Co-Authored-By: Claude (us.anthropic.claude-opus-4-5-20251101-v1:0) <noreply@anthropic.com>

Cargo.toml

@@ -21,6 +21,7 @@ serde_json = "1"
 
 # CLI
 clap = { version = "4", features = ["derive", "env"] }
+clap_complete = "4"
 dialoguer = "0.12"
 console = "0.16"
 indicatif = "0.18"
@@ -46,6 +47,9 @@ flate2 = "1"
 chrono = { version = "0.4", features = ["serde"] }
 uuid = { version = "1", features = ["v4"] }
 
+[target.'cfg(unix)'.dependencies]
+libc = "0.2"
+
 # Logging
 tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }