fix(kyberforge): stop dotfiles-repo $HOME from shadowing user scope

new-agent.sh's walk-up checked for a .git directory before checking
whether it had reached $HOME, so a dotfiles-managed home directory
(e.g. `~/.git` from yadm or a bare-repo checkout) made `new-agent.sh
<name> ~` silently resolve to project scope instead of user scope,
writing .github/agents/ instead of ~/.copilot/agents/. Check the
$HOME boundary before the .git check so it can no longer be shadowed.

Found via post-implementation review of issue #89.

plugins/kyberforge/skills/agent-author/tests/new-agent.bats

@@ -211,6 +211,17 @@ teardown() {
     rm -rf "$FAKE_HOME"
 }
 
+@test "user scope: \$HOME being a dotfiles .git repo does not shadow user scope" {
+    FAKE_HOME="$(mktemp -d)"
+    mkdir "$FAKE_HOME/.git"
+    run env HOME="$FAKE_HOME" bash "$SCRIPT" my-agent "~"
+    assert_success
+    assert [ -f "$FAKE_HOME/.claude/agents/my-agent.md" ]
+    assert [ -f "$FAKE_HOME/.copilot/agents/my-agent.agent.md" ]
+    refute [ -d "$FAKE_HOME/.github" ]
+    rm -rf "$FAKE_HOME"
+}
+
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