docs: /review and /test run in the main session; align review severity labels

docs/agents.md and two persona files said /review and /test wrap the
code-reviewer and test-engineer personas. They invoke a skill in the main
session and spawn nothing (#681). The review commands also still asked for
Critical/Important/Suggestion while the skill and persona use
Critical/Required/Optional/Nit, and /ship named the old labels.

docs/agents.md

@@ -34,10 +34,10 @@ Pick this when you want one perspective on the current change and the user is in
 ### Slash command (single persona behind it)
 Pick this when there's a repeatable workflow you'd otherwise re-explain every time.
 
-- `/review` → wraps `code-reviewer` with the project's review skill
-- `/test` → wraps `test-engineer` with TDD skill
 - `/webperf` → wraps `web-performance-auditor` for performance-focused audits on web apps
 
+`/review` and `/test` are not persona wrappers. They run the `code-review-and-quality` and `test-driven-development` skills in the main session, where the conversation's context is. To get `code-reviewer` or `test-engineer` in a fresh context, invoke the persona directly or run `/ship`.
+
 ### Slash command (orchestrator — fan-out)
 Pick this only when **independent** investigations can run in parallel and produce reports that a single agent then merges.