feat(v2): add safe runtime configuration

docs/superpowers/plans/2026-07-22-t304-go-demo-delivery.md

@@ -41,7 +41,7 @@
 - Create: `v2/assets/runtime-manifest.example.json`
 - Modify: `docs/api.md`
 
-- [ ] **Step 1: Write failing configuration tests**
+- [x] **Step 1: Write failing configuration tests**
 
 ```go
 func TestLoadResolvesOnlyNamedEnvironmentURL(t *testing.T) {
@@ -56,12 +56,12 @@ func TestLoadRejectsEmbeddedRTSPURL(t *testing.T) {
 }
 ```
 
-- [ ] **Step 2: Run the focused test and verify the missing package fails**
+- [x] **Step 2: Run the focused test and verify the missing package fails**
 
 Run: `Set-Location v2; go test ./internal/config -run TestLoad -v`  
 Expected: FAIL because `internal/config` does not exist.
 
-- [ ] **Step 3: Implement the minimal public contract**
+- [x] **Step 3: Implement the minimal public contract**
 
 ```go
 type Config struct {
@@ -79,12 +79,12 @@ func Load(path string) (Config, error) {
 
 Validate all required files and 64-hex model hash before monitoring starts. Return generic path/configuration errors; do not include the resolved URL in errors. Document the V2 field meanings and unchanged `FallEvent` fields in `docs/api.md`.
 
-- [ ] **Step 4: Re-run focused and package tests**
+- [x] **Step 4: Re-run focused and package tests**
 
 Run: `Set-Location v2; go test ./internal/config -v`  
 Expected: PASS, including missing environment, embedded URL, invalid hash and version-redaction cases.
 
-- [ ] **Step 5: Commit the configuration slice**
+- [x] **Step 5: Commit the configuration slice**
 
 ```powershell
 git add v2/config.example.json v2/internal/config v2/assets/runtime-manifest.example.json docs/api.md