claude update warns 'Multiple installations found' when only one installation exists

Description

Running claude update shows a spurious warning about multiple installations found, even though only a single installation exists at the same path.

Warning output

Warning: Multiple installations found
- npm-global at /home/<user>/.local/bin/claude (currently running)
- native at /home/<user>/.local/bin/claude

Root cause (suspected)

The @anthropic-ai/claude-code npm package ships a pre-compiled native ELF binary (bin/claude.exe). The updater's detection logic runs two separate passes: one for npm-global packages and one for native ELF binaries. Since this package satisfies both criteria, it gets reported as two installations despite both entries pointing to the same path.

The _resolved field in the installed package.json is also empty after a clean npm install -g, which may contribute to the detection ambiguity.

Steps to reproduce

1. Install via npm install -g @anthropic-ai/claude-code
2. Run claude update

Expected behavior

No duplicate warning when both detections resolve to the same binary path. The updater should deduplicate by resolved path before warning.

Environment

• OS: Debian GNU/Linux 13 (trixie)
• Architecture: x86-64
• Install method: npm global
• Version: 2.1.185