feat(KIN-010): implement rebuild-frontend post-pipeline hook

- scripts/rebuild-frontend.sh: builds Vue 3 frontend and restarts uvicorn API
- cli/main.py: hook group with add/list/remove/logs/setup commands;
  `hook setup` idempotently registers rebuild-frontend for a project
- agents/runner.py: call run_hooks(event="pipeline_completed") after
  successful pipeline; wrap in try/except so hook errors never block results
- tests: 3 tests for hook_setup CLI + 3 tests for pipeline→hooks integration

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_cli.py

@@ -321,3 +321,34 @@ def test_hook_logs_empty(runner):
     r = invoke(runner, ["hook", "logs", "--project", "p1"])
     assert r.exit_code == 0
     assert "No hook logs" in r.output
+
+
+def test_hook_setup_registers_rebuild_frontend(runner, tmp_path):
+    invoke(runner, ["project", "add", "p1", "P1", "/p1"])
+    r = invoke(runner, ["hook", "setup", "--project", "p1",
+                        "--scripts-dir", str(tmp_path)])
+    assert r.exit_code == 0
+    assert "rebuild-frontend" in r.output
+
+    r = invoke(runner, ["hook", "list", "--project", "p1"])
+    assert r.exit_code == 0
+    assert "rebuild-frontend" in r.output
+    assert "web/frontend/*" in r.output
+
+
+def test_hook_setup_idempotent(runner, tmp_path):
+    invoke(runner, ["project", "add", "p1", "P1", "/p1"])
+    invoke(runner, ["hook", "setup", "--project", "p1", "--scripts-dir", str(tmp_path)])
+    r = invoke(runner, ["hook", "setup", "--project", "p1", "--scripts-dir", str(tmp_path)])
+    assert r.exit_code == 0
+    assert "already exists" in r.output
+
+    r = invoke(runner, ["hook", "list", "--project", "p1"])
+    # Only one hook, not duplicated
+    assert r.output.count("rebuild-frontend") == 1
+
+
+def test_hook_setup_project_not_found(runner):
+    r = invoke(runner, ["hook", "setup", "--project", "nope"])
+    assert r.exit_code == 1
+    assert "not found" in r.output