## Why

Meeting Assistant currently focuses V1 runtime support on Windows capture and Outlook enrichment. We need a separate future change to define macOS and Linux build targets without expanding the V1 scope.

## What Changes

- Define supported macOS and Linux build targets for Meeting Assistant.
- Keep platform-specific capture, hotkey, calendar, and shell integrations isolated per target.
- Ensure non-Windows builds compile without Windows COM, WASAPI, or user32 dependencies.
- Define platform-specific test selection so Windows-only tests do not run on macOS/Linux and future macOS/Linux tests do not run on incompatible targets.

## Impact

- Affected specs: build-targets
- Affected code: project target frameworks, platform service registration, platform integration tests