feat: add Devin CLI support

Devin CLI's `devin plugins install obra/superpowers` fails today because the
repo has no `.devin-plugin/plugin.json` manifest. Add the manifest (skills are
auto-discovered from the co-located skills/ directory), a Devin tool mapping
linked from using-superpowers' Platform Adaptation section, a README install
section, version tracking in .version-bump.json, a Codex-sync exclude for the
new dotdir, and a CI-safe test mirroring the kimi/antigravity test style.

Bootstrap rides Devin's native skill surfacing: every installed skill's
name + description is injected into the system prompt at session start with a
standing instruction to invoke matching skills via the native skill tool.
Acceptance test ("Let's make a react todo list") passes in a clean session:
using-superpowers and brainstorming auto-trigger before any code is written.

README.md

@@ -13,6 +13,7 @@ Superpowers is a complete software development methodology for your coding agent
   - [Codex App](#codex-app)
   - [Codex CLI](#codex-cli)
   - [Cursor](#cursor)
+  - [Devin CLI](#devin-cli)
   - [Factory Droid](#factory-droid)
   - [Gemini CLI](#gemini-cli)
   - [GitHub Copilot CLI](#github-copilot-cli)
@@ -31,7 +32,7 @@ Superpowers is a complete software development methodology for your coding agent
 
 ## Quickstart
 
-Give your agent Superpowers: [Claude Code](#claude-code), [Antigravity](#antigravity), [Codex App](#codex-app), [Codex CLI](#codex-cli), [Cursor](#cursor), [Factory Droid](#factory-droid), [Gemini CLI](#gemini-cli), [GitHub Copilot CLI](#github-copilot-cli), [Grok Build CLI](#grok-build-cli), [Hermes Agent](#hermes-agent), [Kimi Code](#kimi-code), [OpenCode](#opencode), [Pi](#pi).
+Give your agent Superpowers: [Claude Code](#claude-code), [Antigravity](#antigravity), [Codex App](#codex-app), [Codex CLI](#codex-cli), [Cursor](#cursor), [Devin CLI](#devin-cli), [Factory Droid](#factory-droid), [Gemini CLI](#gemini-cli), [GitHub Copilot CLI](#github-copilot-cli), [Grok Build CLI](#grok-build-cli), [Hermes Agent](#hermes-agent), [Kimi Code](#kimi-code), [OpenCode](#opencode), [Pi](#pi).
 
 ## How it works
 
@@ -128,6 +129,20 @@ Superpowers is available via the [official Codex plugin marketplace](https://git
 
 - Or search for "superpowers" in the plugin marketplace.
 
+### Devin CLI
+
+- Install the plugin from this repository:
+
+  ```bash
+  devin plugins install obra/superpowers
+  ```
+
+- Update to the latest version with:
+
+  ```bash
+  devin plugins update superpowers
+  ```
+
 ### Factory Droid
 
 - Register the marketplace: