fix(installer): quote model metadata in generated env

[tang-vu]

Summary

• quote installer-managed model recommendation metadata in generated dotenv files
• keep Linux, macOS, and Windows env generators on the same contract
• verify the real Linux-generated .env can be sourced with spaces, parentheses, and semicolon-separated alternatives

Why this matters

Closes #2617. The production hardware/model selection path writes MODEL_RECOMMENDATION_REASON, MODEL_RECOMMENDED_ALTERNATIVES, and MODEL_PERFORMANCE_LABEL into .env. Those values contain shell-significant spaces, parentheses, and semicolons. Unquoted output made source .env fail and could interpret alternative model entries as commands, preventing operators from loading API keys and other settings after installation.

Overlap check

Searched open and closed PRs for MODEL_RECOMMENDATION_REASON env quote, MODEL_RECOMMENDED_ALTERNATIVES, multiline env, issue #2617, and the three platform env generators. No existing PR covers model-metadata dotenv quoting. The scope is independent of recent atomic-write and sed-escaping changes because it fixes the generated value grammar itself.

Test plan

• bash -n ods/installers/phases/06-directories.sh ods/installers/macos/lib/env-generator.sh ods/tests/smoke/installer-env-smoke.sh
• bash ods/tests/smoke/installer-env-smoke.sh — model-metadata, schema, dependency, and compose checks pass; existing unrelated phase-07 ai_err function-resolution check fails
• PowerShell parser accepts ods/installers/windows/lib/env-generator.ps1
• git diff --check

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