test: split monolithic test file into tests directory

docs: simplify pre-push hook section

docs: update README intro to match current feature set

refactor: add a manual review note for dependency findings

docs: note that siftr is experimental

docs: make scope and limitations more user-focused

feat: detect unused dependencies and devDependencies

refactor: improve report readability

feat: report default exports in a separate review section

chore: remove unused internal exports

chore: refine package scripts and format code with oxfmt

chore: add pre-push verify hook and document setup

chore: rename CLI from sift to siftr

feat: add minimal CLI for finding unused exports