0005: Controlled tag vocabulary in docs/tags.md
Context: Free tags fragment (test, tests, testing) and stop being useful for lookup.
Decision: Tags only from docs/tags.md, one line each with meaning.
A new tag is added there in the same change. Tools show existing tags when adding.
Consequences: Tag lookup is reliable; vocabulary is checkable. Small friction to add a tag. → reflected in architecture: docs layout.
Alternatives: | option | why not | |---|---| | free-form tags | synonyms and typos; lookup fails | | directory hierarchy only | one file belongs to several topics | | no tags | agents can't find related docs without reading all |