Add oracle harness: verb goldens and function-level vectors

Records stdout/stderr/exit/files for every impeccable verb over a fixed
corpus and replays them against an alternate implementation. Adds a loader
hook that captures per-function call vectors from the pure engine modules.

Prepared with AI assistance (Claude Code).

tests/oracle/golden/cli-help.json

@@ -0,0 +1,7 @@
+{
+  "stdout": "Usage: impeccable <command> [options]\n\nCommands:\n  detect [file-or-dir-or-url...]   Scan for UI anti-patterns and design quality issues\n  ignores                          Manage detector ignore rules, files, and values\n  help                             List all available skills and commands\n  install                          Install impeccable skills into your project or global harness\n  link                             Symlink skills from a local checkout or submodule\n  update                           Update skills to the latest version\n  check                            Check if skill updates are available\n\nOptions:\n  --help       Show this help message\n  --version    Show version number\n\nCompatibility:\n  impeccable skills <command>       Legacy namespace; still supported.\n",
+  "stderr": "",
+  "exit": 0,
+  "signal": null,
+  "files": {}
+}