engager 0.1.0

Initial CRAN Submission

• Renamed the package from zoomstudentengagement to engager.
• Added core transcript loading, processing, summarization, plotting, privacy masking, and metric writing workflows for Zoom/WebVTT transcripts.
• Added an exact name-matching MVP with privacy-safe unresolved-name export: detect_unmatched_names(), match_names_workflow(), and write_unresolved().
• Added privacy review helpers and documentation with explicit institutional-review caveats.
• Limited the supported v0.1.0 identifier transformations to masking, hashing with an explicit caller-provided salt, and pseudonymization. Missing and blank identifiers remain missing or blank; unsafe aggregation is rejected.
• Kept multi-session attendance and attendance-report generation internal until their roster, threshold, and chart semantics receive installed-workflow UAT.
• Made CSV metric exports omit raw transcript/comment text by default; raw comments now require an explicit local-review export with privacy disabled.
• Added release validation targets for R CMD check, exported API coverage, lint, build, tarball inspection, and performance regression review.