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.lock

@@ -211,6 +211,15 @@ dependencies = [
  "strsim",
 ]
 
+[[package]]
+name = "clap_complete"
+version = "4.5.65"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "430b4dc2b5e3861848de79627b2bedc9f3342c7da5173a14eaa5d0f8dc18ae5d"
+dependencies = [
+ "clap",
+]
+
 [[package]]
 name = "clap_derive"
 version = "4.5.49"
@@ -1085,6 +1094,7 @@ dependencies = [
  "async-stream",
  "chrono",
  "clap",
+ "clap_complete",
  "comfy-table",
  "console",
  "dialoguer",
@@ -1092,6 +1102,7 @@ dependencies = [
  "flate2",
  "futures",
  "indicatif",
+ "libc",
  "open",
  "rand",
  "reqwest",