* docs(manual): add introduction page
* docs(manual): rewrite getting started as guided first run
* docs(manual): rewrite writing specs as a folio tutorial
* docs(manual): document missing spec API in reference
* docs(manual): plain-language rewrite of runs page
* docs: real introductions on index pages and README
* fix(docs): sibling links from directory-style pages need ../
* fix(docs): correct sampling and restart-cost claims to match implementation
* docs: nav lists Introduction and Case study; roadmap points to milestone
* docs(manual): make getting started target the reader's own app, not Folio
* docs(manual): add Folio case study page
* docs: point manual navigation at the case study
* docs(readme): lead with the case study, fix roadmap link
* docs: roadmap links to milestone, sync clear-data default and cross-links
* refactor: rename inspect to replay across the codebase
Renames inspect-ui/ to replay-ui/, internal/inspect/ to internal/replay/,
the CLI subcommand from `sanderling inspect` to `sanderling replay`, and
updates all references in docs, Makefile, README, and Go comments.
* feat(replay-ui): show spec filename with full path on hover
RunList and RunDetail now render the basename of spec_path (e.g.
login.spec.ts) with the full path available as a title tooltip.
pj