Add daemon-backed indexing and search

[plumocracy]

Summary

• add daemon commands and install/start scripts for background indexing
• index changed files incrementally with historical chunk storage
• route daemon search/dry-run through the shared ranking path with caching, temporal filtering, and stricter top-level navigation behavior

Tests

• cargo fmt
• cargo test --lib collapses_single_leaf_term_to_general_directory
• cargo test --all
• cargo clippy --all-targets --all-features -- -D warnings