Single-skill module

Read this when the user has, or wants, one skill that bmad should know about: set it up, recommend it from help, check it for updates.

One folder is both the skill and its module record. Its bmod.toml carries a [bmod] table (code, version, update source, required skills, optional configuration questions, install messages) and an empty [skill] table that says the module's one skill is this folder. A help/help.md beside it tells the bmad help agent what the skill gives and when to recommend it. The folder keeps the skill's name; bmad finds the module by the [bmod] table.

What it gives over a plain skill: bmad setup <code> asks its questions and the skill reads the answers as modules.<code>.<key>; bmad help recommends it; update checks follow its source; another skill can require it by name. It is the default offer for a lone skill that needs a project-level answer (an output folder, a file it maintains, a style) or that the user simply wants registered. A skill with nothing to ask drops the questions block rather than shipping a placeholder question.

If a second skill arrives later, the record moves to a bmod-<code>/ folder and both become members (help/shape-multi-skill-module.md). Package mode does that move.