Cover the remaining paths in the client, context, downloads, title
generation, document tools and store models, and add fail_under=100 so
uncovered lines fail CI.
Six lines that no test can reach get a pragma with its reason: the docling
import guard, the nameless PDF attachment, the FS symlink OSError guard that
resolve(strict=False) absorbs, the docling bbox and LanceDB document-id
shape guards, the tag-retention branch vacuum makes unreachable, and Monty's
Rust-thread print callback.
Fix test_find_config_file_user_config, which wrote its config into the cwd it
had chdir'd to, so the cwd branch answered first and the user-directory
lookup it names was never exercised.
