Add working conventions to CLAUDE.md

Ask when unclear, script repeated tasks, and require automated tests
with every feature or fix.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CLAUDE.md

@@ -7,3 +7,12 @@ library (`nisse-core`), one package per directory.
 specification is `docs/Architecture-Build-Spec.md`. Requirements that look like
 free choices — gating structure, state durability, LLM access paths, permission
 policy — are usually settled there.
+
+## Working conventions
+
+- **Ask when anything is unclear.** Do not assume the operator always knows
+  exactly what they want; surfacing ambiguity beats guessing.
+- **Script repeated tasks.** If a job takes the same multiple commands more than
+  once, save it as a shell script (e.g. in `~/bin`) instead of retyping it.
+- **Strongly prefer automated tests over manual testing.** Every new feature or
+  bug fix includes at least one new test verifying its behavior.