refactor(beaver): 移除Hermes相关引用和迁移代码，完善Beaver后端主线实现

移除了所有Hermes相关的命名引用，包括：
- 从.gitignore中清理相关构建缓存文件
- 将README中的beaver-home路径配置更新
- 完善backend/README.md文档说明Beaver后端主线实现
- 移除Hermes风格的相关注释和兼容性代码
- 清理nanobot环境变量兼容性处理
- 删除技能迁移和服务迁移相关功能代码
- 更新测试用例中相关命名和函数名

BREAKING CHANGE: 移除了Hermes迁移相关API和CLI命令，不再支持nanobot环境变量兼容性

app-instance/backend/beaver/interfaces/cli/main.py

@@ -1,7 +1,5 @@
 """CLI entry for Beaver."""
 
-from pathlib import Path
-
 try:
     import typer
 except ModuleNotFoundError:  # pragma: no cover - fallback for skeleton-only environments
@@ -29,8 +27,6 @@ except ModuleNotFoundError:  # pragma: no cover - fallback for skeleton-only env
     typer = _FallbackTyper()  # type: ignore[assignment]
 
 from beaver.services.agent_service import AgentService
-from beaver.services.hermes_migration import HermesMigrationService
-from beaver.skills.specs import SkillSpecStore
 
 app = typer.Typer(help="Beaver backend CLI") if hasattr(typer, "Typer") else typer
 
@@ -59,26 +55,6 @@ def run(
     typer.echo(result.output_text)
 
 
-@app.command("migrate-hermes")
-def migrate_hermes(
-    repo: str = typer.Option(..., "--repo", help="Local checkout of https://github.com/NousResearch/hermes-agent."),
-    workspace: str | None = typer.Option(None, "--workspace", help="Workspace root to import skills into."),
-    manifest: str | None = typer.Option(None, "--manifest", help="Path for hermes_migration_manifest.json."),
-    dry_run: bool = typer.Option(False, "--dry-run", help="Only write the manifest without importing skills."),
-) -> None:
-    """Import no-credential Hermes Agent skills and write a manifest."""
-
-    service = AgentService(workspace=workspace)
-    loaded = service.create_loop().boot()
-    store = loaded.skill_spec_store or SkillSpecStore(loaded.workspace)
-    migration = HermesMigrationService(store, manifest_path=Path(manifest) if manifest else None)
-    result = migration.migrate(repo, dry_run=dry_run)
-    typer.echo(
-        f"Hermes migration complete: {len(result['included'])} included, "
-        f"{len(result['skipped'])} skipped."
-    )
-
-
 def main() -> None:
     """Project script entrypoint."""
     app()