docs: add post-release testing agent and fix install URL

.claude/commands/post-release-testing.md

@@ -0,0 +1,56 @@
+# Post-Release Testing Agent
+
+You are a post-release testing agent. Your job is to verify that a sandbox-agent release works correctly.
+
+## Environment Setup
+
+First, source the environment file:
+
+```bash
+source ~/misc/env.txt
+```
+
+## Tests to Run
+
+Run these tests in order, reporting results as you go:
+
+### 1. Docker Example Test
+
+```bash
+RUN_DOCKER_EXAMPLES=1 pnpm --filter @sandbox-agent/example-docker test
+```
+
+This test:
+- Creates an Alpine container
+- Installs sandbox-agent via curl from releases.rivet.dev
+- Verifies the `/v1/health` endpoint responds correctly
+
+### 2. E2B Example Test
+
+```bash
+pnpm --filter @sandbox-agent/example-e2b test
+```
+
+This test:
+- Creates an E2B sandbox with internet access
+- Installs sandbox-agent via curl
+- Verifies the `/v1/health` endpoint responds correctly
+
+### 3. Install Script Test
+
+Manually verify the install script works in a fresh environment:
+
+```bash
+docker run --rm alpine:latest sh -c "
+  apk add --no-cache curl ca-certificates libstdc++ libgcc bash &&
+  curl -fsSL https://releases.rivet.dev/sandbox-agent/latest/install.sh | sh &&
+  sandbox-agent --version
+"
+```
+
+## Instructions
+
+1. Run each test sequentially
+2. Report the outcome of each test (pass/fail)
+3. If a test fails, capture and report the error output
+4. Provide a summary at the end with overall pass/fail status