chore: remove stories/checker backend dead code

Remove the dead stories/checker backend tracked as design debt in CLAUDE.md:
- Delete internal/api/stories.go, stories_test.go, elaborate.go
- Delete internal/task/story.go, story_test.go
- Remove story/checker columns from storage schema and all CRUD methods
- Remove checkStoryCompletion, spawnCheckerTask, triggerStoryDeploy,
  createValidationTask, checkValidationResult, ShipStory, CheckStoryCompletion
  from executor; simplify handleRunResult
- Remove story/checker fields from task.Task (StoryID, AcceptanceCriteria,
  CheckerForTaskID, CheckerReport)
- Remove story routes and geminiBinPath from API server
- Move claudeJSONResult/extractJSON from elaborate.go to validate.go
- Rename ensureStoryBranch -> ensureBranch in ContainerRunner
- Fix git identity in bare-repo tests; fix initial-branch to use main

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/internal/api/agentmcp_endpoint_test.go b/internal/api/agentmcp_endpoint_test.go
index b2f77d3..b9cee3a 100644
--- a/internal/api/agentmcp_endpoint_test.go
+++ b/internal/api/agentmcp_endpoint_test.go
@@ -52,7 +52,7 @@ func TestServer_MountsAgentMCPEndpoint(t *testing.T) {
 	fc := &fakeAgentChannel{}
 	token, _ := reg.Mint(fc)
 
-	srv := NewServer(store, pool, reg, logger, "claude", "gemini")
+	srv := NewServer(store, pool, reg, logger, "claude")
 	ts := httptest.NewServer(srv.Handler())
 	defer ts.Close()
 
@@ -87,7 +87,7 @@ func TestServer_NoRegistry_NoMCPRoute(t *testing.T) {
 	pool := executor.NewPool(1, map[string]executor.Runner{}, store, logger)
 
 	// nil registry → /mcp must not be mounted.
-	srv := NewServer(store, pool, nil, logger, "claude", "gemini")
+	srv := NewServer(store, pool, nil, logger, "claude")
 	ts := httptest.NewServer(srv.Handler())
 	defer ts.Close()