feat: add developer skill — coding conventions + architecture guide

Adds 'uwf skill developer' for contributors to the workflow engine.
Covers: monorepo structure, dependency layers, functional-first conventions,
error handling, logging with tagged logger, development workflow,
testing, publishing, key modules (moderator, extract pipeline, createAgent).

Refs #541

packages/cli-workflow/src/cli.ts

@@ -21,6 +21,7 @@ import {
   cmdSkillArchitecture,
   cmdSkillAuthor,
   cmdSkillCli,
+  cmdSkillDeveloper,
   cmdSkillList,
   cmdSkillModerator,
   cmdSkillUser,
@@ -520,6 +521,13 @@ skill
     console.log(cmdSkillAuthor());
   });
 
+skill
+  .command("developer")
+  .description("Print the developer reference (coding conventions + architecture)")
+  .action(() => {
+    console.log(cmdSkillDeveloper());
+  });
+
 skill
   .command("moderator")
   .description("Print the moderator reference")