feat: Add official support for Android/Termux

[Rogercode97]

Description

Currently, Gentle-AI blocks execution on Android/Termux with an 'unsupported operating system' error. After investigating and patching the source code locally, I've confirmed that Gentle-AI works perfectly on Termux if the OS check is bypassed and the binary is compiled from source.

Proposed Changes

1. internal/system/detect.go: Add android to IsSupportedOS function.
2. internal/system/detect.go: Add case "android": to resolvePlatformProfile and set profile.Supported = true.
3. internal/system/guard.go: Ensure android doesn't trip the Linux distro validation.

Why this is important

Many users use Termux as their primary mobile development environment. Enabling official support would allow them to use the full power of Gentle-AI workflows on the go.

I have already tested these changes on an arm64 Android device running Termux and everything (CLI/TUI) works as expected.

[Alan-TheGentleman]

Closing as duplicate of #276 — same scope: native Termux / Android support. PR #277 (by @Snakeblack) is already in flight against #276. Tracking there.