fix: force base-10 in version_gte to prevent octal interpretation

Use 10#$var arithmetic prefix to avoid bash interpreting leading
zeros as octal (e.g., 08 or 09 would cause "value too great for
base" errors). 2 new tests (64 total).

Closes: #9

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

test/git-harden.bats

@@ -108,6 +108,18 @@ source_functions() {
     assert_failure
 }
 
+@test "version_gte: handles leading zeros without octal error" {
+    source_functions
+    run version_gte "2.08.0" "2.07.0"
+    assert_success
+}
+
+@test "version_gte: leading zero comparison works correctly" {
+    source_functions
+    run version_gte "2.09.1" "2.09.0"
+    assert_success
+}
+
 # ===========================================================================
 # Version extraction (grep-based, not sed)
 # ===========================================================================