docs: enhance getting-started, hardware, and project collection indexes

Adds onboarding decision tree to getting-started/README.md so users can
quickly identify the right setup command for their situation.

Adds hardware vision overview to hardware/README.md explaining the
Peripheral trait and supported board types.

Expands project/README.md with scope explanation describing the purpose
of project snapshots and how they relate to documentation maintenance.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

docs/getting-started/README.md

@@ -8,6 +8,15 @@ For first-time setup and quick orientation.
 2. One-click setup and dual bootstrap mode: [../one-click-bootstrap.md](../one-click-bootstrap.md)
 3. Find commands by tasks: [../commands-reference.md](../commands-reference.md)
 
+## Choose Your Path
+
+| Scenario | Command |
+|----------|---------|
+| I have an API key, want fastest setup | `zeroclaw onboard --api-key sk-... --provider openrouter` |
+| I want guided prompts | `zeroclaw onboard --interactive` |
+| Config exists, just fix channels | `zeroclaw onboard --channels-only` |
+| Using subscription auth | See [Subscription Auth](../../README.md#subscription-auth-openai-codex--claude-code) |
+
 ## Onboarding and Validation
 
 - Quick onboarding: `zeroclaw onboard --api-key "sk-..." --provider openrouter`