v2.1.3 - Installer NativeCommandError fix across the per-agent adapters

Patch release: finishes the installer stderr fix started in v2.1.2. Urgent.

Fixed

• The per-agent installers had the same NativeCommandError bug as the shared one. agents/claude/install.ps1 and agents/codex/install.ps1 clone the node-building skills (and codex registers its MCP) with & git clone ... 2>&1 | Out-Null / & codex mcp add ... 2>&1 | Out-Null under $ErrorActionPreference = "Stop", so a harmless native stderr line could abort the adapter install (v2.1.2 fixed only the shared installer). Both now route those calls through the Native helper. The gemini / qwen adapters make no native calls and were unaffected.
• Installer catches a partial template clone instead of reporting success. shared/install_shared.ps1 now gates the "cloned + index built" message on the exit codes of all three git steps (clone / sparse-checkout / checkout), not just a Test-Path index.json check, so a partial clone falls through to the "template clone incomplete" warning.