Adding packages/util/brand/ created a new top-level packages/util/ group that
the hierarchy/dependency docs never enumerated. Document it:
- Add packages/util/README.md, the group README (low-level zero-dependency
utilities shared across groups; lists dsh-brand).
- packages/README.md: add the util/ group to the group table, dsh-brand to the
package table, and dsh-brand to the dependency graph. Correct the now-false
"no harness deps" claims — dsh-llm and dsh-bash both depend on dsh-brand
(verified dsh-bash imports Branded from dsh-brand, not dsh-llm; dsh-session
and dsh-agent depend on it too).
- Root AGENTS.md Repository Layout: add the util/ group with brand/.
Align the implemented branded-ids RFC with what shipped: Branded lives in
@deepseek-ai/dsh-brand (packages/util/brand/), and dsh-bash depends only on
that utility package instead of dsh-llm. Fix the BashTaskId import source, the
illustrative snippet, and the opening policy reference (now dsh-brand).
