Generate Conventions

1. Read the bar

docs/CONVENTIONS.md must exist. If it doesn't, run scaffold-docs first. Its "What belongs in a convention file" section governs everything below. Read the existing docs/conventions/ files too: a rule that fits one of them is an edit.

2. Gather candidates

Each candidate needs evidence in the code, and you don't get to invent the project's position. Skip anything a survey already answers: the stack, the layout, the actions a controller happens to have. That's architecture.

Taste