v1.8.0: Unified config resolution (projectRoot required)

What changed

All six tools now resolve .aireadme.config.json the same way — loadConfig(projectRoot), reading config from the explicit project root. No walking up, no guessing.

compress_ai_readme and update_ai_readme previously lacked a projectRoot and had to infer it from the file path. v1.7.3 made them walk up the directory tree, which fixed nested READMEs but could read a config above the project (e.g. in $HOME) and left them with a different config-lookup path than the other four tools. This release unifies the behavior instead.

• compress_ai_readme / update_ai_readme now require projectRoot and read config exactly like get_context_for_file / discover_ai_readmes / validate_ai_readmes / init_ai_readme.
• Removed the loadConfigNearest / loadConfigFor guessing helpers (and their tests).

⚠️ Breaking

Callers of compress_ai_readme / update_ai_readme must now pass projectRoot. This parameter was never published to npm (the registry is at 1.7.2), so no released public API depended on its absence — hence a minor bump rather than a major one.