Fix npm prefix to use environment variable for nvm compatibility

[Copilot]

Description

The opencode module used npm config set prefix which persists to ~/.npmrc, causing nvm to fail with "prefix setting, which are incompatible with nvm" errors when users install both modules.

Changed to NPM_CONFIG_PREFIX environment variable - achieves same install location without modifying ~/.npmrc.

Type of Change

• New module
• New template
• Bug fix
• Feature/enhancement
• Documentation
• Other

Module Information

Path: registry/rothnic/modules/opencode
New version: v1.0.1
Breaking change: [ ] Yes [x] No

Testing & Validation

• Tests pass (bun test)
• Code formatted (bun fmt)
• Changes tested locally

Verification:

# Old approach - creates ~/.npmrc (breaks nvm)
npm config set prefix "$HOME/.local"
cat ~/.npmrc  # Shows: prefix=/home/user/.local

# New approach - no ~/.npmrc modification (nvm compatible)
export NPM_CONFIG_PREFIX="$HOME/.local"
npm config get prefix  # Shows: /home/user/.local
cat ~/.npmrc  # File doesn't exist or unchanged

Related Issues

Fixes workspace startup failures when using both opencode and nodejs modules with nvm.

Original prompt

The opencode module installation script (registry/rothnic/modules/opencode/scripts/install.sh) currently runs npm config set prefix "$HOME/.local". This creates or modifies ~/.npmrc with a global prefix setting.

When a user also uses nvm (e.g., via the nodejs module), nvm fails if a prefix is set in ~/.npmrc, causing workspace startup errors like:
prefix setting, which are incompatible with nvm.

To fix this, modify registry/rothnic/modules/opencode/scripts/install.sh to:

1. Remove the npm config set prefix command.
2. Instead, set export NPM_CONFIG_PREFIX="$HOME/.local" in the install_opencode function before running npm install.
3. Ensure opencode installs correctly to ~/.local without persisting the prefix in ~/.npmrc.

This pull request was created as a result of the following prompt from Copilot chat.

The opencode module installation script (registry/rothnic/modules/opencode/scripts/install.sh) currently runs npm config set prefix "$HOME/.local". This creates or modifies ~/.npmrc with a global prefix setting.

When a user also uses nvm (e.g., via the nodejs module), nvm fails if a prefix is set in ~/.npmrc, causing workspace startup errors like:
prefix setting, which are incompatible with nvm.

To fix this, modify registry/rothnic/modules/opencode/scripts/install.sh to:

1. Remove the npm config set prefix command.
2. Instead, set export NPM_CONFIG_PREFIX="$HOME/.local" in the install_opencode function before running npm install.
3. Ensure opencode installs correctly to ~/.local without persisting the prefix in ~/.npmrc.

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