fix(kyberforge): stop dotfiles-repo $HOME from shadowing user scope in validate.sh

detect_scope() had the same bug class fixed in new-agent.sh (099bdec):
it checked for a .git directory before checking whether it had reached
$HOME, so a dotfiles-managed home directory (yadm, chezmoi bare-repo,
etc.) made validate.sh misresolve to project scope, deriving the
counterpart as ~/.github/agents/<name>.agent.md instead of the correct
~/.copilot/agents/<name>.agent.md and failing with a false "counterpart
file not found". Check the $HOME boundary before the .git check, same
fix shape as 099bdec.

Found via post-implementation review of issue #89.

plugins/kyberforge/skills/agent-audit/tests/validate.bats

@@ -68,6 +68,30 @@ EOF
     refute_output --partial "FAIL"
 }
 
+@test "user scope: \$HOME being a dotfiles .git repo does not shadow user scope" {
+    local fake_home="$TMPDIR/fakehome"
+    mkdir -p "$fake_home/.git" "$fake_home/.claude/agents" "$fake_home/.copilot/agents"
+    cat > "$fake_home/.claude/agents/my-agent.md" <<EOF
+---
+name: my-agent
+description: A valid agent description.
+---
+
+You are a test agent. When invoked, do the thing.
+EOF
+    cat > "$fake_home/.copilot/agents/my-agent.agent.md" <<EOF
+---
+name: my-agent
+description: A valid agent description.
+---
+
+You are a test agent. When invoked, do the thing.
+EOF
+    run env HOME="$fake_home" bash "$SCRIPT" "$fake_home/.claude/agents/my-agent.md"
+    assert_success
+    refute_output --partial "FAIL"
+}
+
 @test "--help exits 0 and shows Usage:" {
     run bash "$SCRIPT" --help
     assert_success