Installer: Silent and Unattended Install Mode

[itomek]

Problem

The current installer (#530) targets interactive user-driven installation only. For deploying Gaia on devices without user interaction — such as automated setups or pre-configured images — the installer must support an unattended/silent mode that requires no UI prompts.

Proposed Changes

1. Silent Install Mode

Extend the desktop installer (#530) with:

• --silent or /S flag for fully unattended installation
• All configuration sourced from command-line flags or an embedded deployment profile (Deployment Configuration Profiles #613) — no prompts
• Standardized exit codes for success/failure (for use in scripts and automation tools)
• Log file written to a standard location for troubleshooting

2. Session-Independent Installation

• Installer can run without a logged-in user session
• Gaia installs to the correct location and first-run onboarding (feat(agent-ui): first-run setup wizard / onboarding flow #597) triggers on the user's first launch

3. Bundled Model Support

• Installer optionally bundles or downloads the target model during setup
• Bundled: Model included in the installer package — larger download, no post-install fetch
• Downloaded: Installer fetches the model during install with progress reporting
• Model selection driven by the embedded deployment profile

Files Likely Affected

• src/gaia_ui/electron/ — installer scripts (NSIS/DMG), silent mode flags
• Build scripts — packaging configurations with/without bundled model

Acceptance Criteria

• Silent install completes without any UI prompts
• Exit codes correctly report success and failure
• Install log written to a predictable location
• Installation works without an active user session
• Bundled model option skips post-install model download
• Downloaded model option fetches during install with progress reporting

References

• Extends: Desktop installer: one-click install with NSIS, DMG, AppImage + auto-update #530 (Desktop installer: one-click install)
• Related: Deployment Configuration Profiles #613 (Deployment configuration profiles)
• Related: Update Lemonade installer and version gating for v10 (DEB naming, Linux NPU) #533 (Update Lemonade installer and version gating)