feat: add presence skill — visible value, not noise

Defines how ArcheFlow communicates: compact status lines per phase,
show outcomes not mechanics, silence for clean passes. One-line
activation indicator at session start.

skills/using-archeflow/SKILL.md

@@ -7,6 +7,16 @@ description: Use at session start when implementing features, reviewing code, de
 
 Multi-agent orchestration using archetypal roles and PDCA quality cycles.
 
+## Session Start
+
+On activation, print ONE line:
+```
+archeflow v0.3.0 · 25 skills · <domain> domain
+```
+Where `<domain>` is auto-detected: `writing` if `colette.yaml` exists, `research` if paper/thesis files exist, `code` otherwise. Then proceed silently — no further announcement unless `archeflow:run` is invoked.
+
+During runs, follow the `archeflow:presence` skill for output format: show outcomes not mechanics, one line per phase, value at the end.
+
 ## IMPORTANT: When to Activate
 
 You MUST use ArcheFlow orchestration (load `archeflow:orchestration` skill and follow its steps) for any task that matches: