refactor: refocus ArcheFlow as workspace orchestrator, not feature-dev competitor

- README: lead with af-sprint (parallel multi-project), af-review (post-impl quality)
- Sprint skill: L/XL code tasks use feature-dev style (explore→plan→impl→self-review)
  instead of PDCA. Reserve PDCA for writing/research domains.
- Session start: route to af-sprint/af-review/af-run based on task type
- Explicitly state: for single-feature dev, use feature-dev plugin instead

skills/using-archeflow/SKILL.md

@@ -17,16 +17,27 @@ Where `<domain>` is auto-detected: `writing` if `colette.yaml` exists, `research
 
 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
+## IMPORTANT: When to Use What
 
-You MUST use ArcheFlow orchestration (load `archeflow:orchestration` skill and follow its steps) for any task that matches:
+### Use `/af-sprint` (primary mode) when:
+- User says "run the sprint", "work the queue", "go autonomous"
+- Multiple tasks are pending across projects
+- The workspace queue (docs/orchestra/queue.json) has pending items
 
-- **New features** -- any feature touching 2+ files
-- **Refactoring** -- structural changes across modules
-- **Security-sensitive changes** -- auth, encryption, input handling, API keys
-- **Bug fixes with unclear root cause** -- use Explorer to investigate first
-- **Code review requests** -- spawn Guardian + relevant reviewers
-- **Multi-file changes** -- anything beyond a single-file edit
+### Use `/af-review` when:
+- User wants to review code before merging
+- A diff, branch, or commit range needs quality check
+- Security-sensitive changes need Guardian analysis
+
+### Use `/af-run` (deep orchestration) when:
+- **Writing/research tasks** -- archetypes add value where linters don't exist
+- **Security-sensitive code changes** -- auth, encryption, API keys
+- **Complex multi-module refactors** with unclear approach
+
+### Do NOT use ArcheFlow for:
+- **Single-feature code development** -- use `feature-dev` plugin or work directly
+- **Simple fixes** -- just do them
+- **Questions, exploration, reading** -- no code changes needed
 
 Choose the workflow based on risk: