refactor: discriminated union frontmatter for solve-issue workflow

- planner: oneOf ready (plan, repoPath) | insufficient_info
- developer: single exit, plain object (branch, worktree), no $status
- reviewer: oneOf approved (branch, worktree) | rejected (comments)
- tester: oneOf passed (branch, worktree) | fix_code (report) | fix_spec (report)
- committer: oneOf committed (prUrl) | hook_failed (error)
- Edge prompts now use mustache templates with variant-specific fields
- Developer simplified from 2 exits to single exit (unit routing)

Phase 2 of #499 (closes #501)

packages/cli-workflow/src/__tests__/solve-issue-tea-worktree.test.ts

@@ -81,17 +81,18 @@ describe("solve-issue workflow: tea pr create worktree fix", () => {
     expect(workflow.roles.committer?.frontmatter).toBeDefined();
   });
 
-  test("committer frontmatter schema should require $status field", async () => {
+  test("committer frontmatter schema should be oneOf with $status discriminant", async () => {
     const yamlContent = await readFile(workflowPath, "utf-8");
     // Parse as any to access the raw YAML structure (frontmatter is inline JSON Schema in YAML)
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     const workflow = parse(yamlContent) as any;
-
     const frontmatter = workflow.roles.committer?.frontmatter;
     expect(frontmatter).toBeDefined();
-    expect(frontmatter?.type).toBe("object");
-    expect(frontmatter?.properties?.["$status"]).toBeDefined();
-    expect(frontmatter?.properties?.["$status"]?.enum).toContain("committed");
-    expect(frontmatter?.required).toContain("$status");
+    expect(frontmatter?.oneOf).toBeDefined();
+    const committedVariant = frontmatter.oneOf.find(
+      (v: any) => v.properties?.["$status"]?.const === "committed",
+    );
+    expect(committedVariant).toBeDefined();
+    expect(committedVariant.required).toContain("$status");
   });
 });