chore: consolidate plugin for sharing

- Add .gitignore (ignore .archeflow/ runtime state)
- Move custom archetype examples from .archeflow/ to examples/
- Remove onboarding skill (covered by using-archeflow + README)
- Remove internal planning doc
- Clean roadmap (remove tool.archeflow references)
- Simplify session-start hook config
- Polish README for external users

skills/onboarding/SKILL.md

@@ -1,46 +0,0 @@
----
-name: onboarding
-description: Use when a user is new to ArcheFlow or asks "what is this?" / "how does this work?". Explains the plugin in 60 seconds.
----
-
-# Welcome to ArcheFlow
-
-ArcheFlow is a Claude Code plugin that automatically coordinates multiple AI agents when you give implementation tasks. Instead of one agent doing everything, specialized agents with different perspectives collaborate through quality cycles.
-
-## What Just Happened
-
-When you installed ArcheFlow, it activated automatically. From now on:
-
-- **Give an implementation task** (feature, refactor, bug fix) → ArcheFlow kicks in
-- **Give a quick task** (typo fix, question, config edit) → Claude handles it normally
-
-You don't need to do anything different. Just describe your task.
-
-## The 30-Second Version
-
-```
-You: "Add user authentication with JWT"
-
-ArcheFlow:
-  🔍 Explorer researches your codebase (what files, what patterns, what tests)
-  <20><>️ Creator designs a proposal (architecture, file changes, test strategy)
-  ⚒️ Maker implements it in a safe branch (isolated, nothing breaks)
-  🛡️ Guardian reviews for security (injection, auth bypass, data exposure)
-  🤔 Skeptic challenges assumptions (what if JWT isn't the right choice?)
-  📚 Sage checks quality (readable? tested? consistent with codebase?)
-  ✅ All approve → merged. Issues? → automatic revision cycle.
-```
-
-## Key Concepts
-
-- **Archetypes:** 7 specialized agent roles, each with a unique perspective
-- **PDCA Cycles:** Plan → Do → Check → Act. If reviewers reject, it cycles back and improves
-- **Worktrees:** Code changes happen on isolated branches. Nothing touches main until approved.
-- **Shadow Detection:** If an agent gets stuck or dysfunctional, ArcheFlow detects and corrects it
-- **Workflows:** `fast` (1 cycle, quick fixes), `standard` (2 cycles, features), `thorough` (3 cycles, security)
-
-## Want to Learn More?
-
-- `/archeflow:orchestration` — See the full step-by-step execution guide
-- `/archeflow:shadow-detection` — How dysfunction is detected and corrected
-- `/archeflow:autonomous-mode` — Run tasks overnight unattended