fix: preserve leading dots in .cceignore paths

[MDerman]

Summary

• preserve leading dots when normalizing .cceignore paths
• add matcher and indexing-pipeline regression coverage for root-level dot-directories

Problem

str.lstrip("./") removes every leading dot or slash, rather than only the exact ./ prefix. A root path such as .playwright therefore became playwright and no longer matched a .playwright/ ignore pattern.

Testing

• direct matcher checks for .playwright, ./.playwright, .env, and existing directory-only behavior
• python3 -m py_compile src/context_engine/indexer/ignorefile.py tests/indexer/test_ignorefile.py
• full pytest matrix left to CI because the local CCE development dependencies are not installed

Prepared with OpenAI Codex (GPT-5).

[MDerman]

@fazleelahhee we just getting large indexes as a result of folders that I prefix with .