Uninstall, and the macOS paths in INSTALL.md #315

Part of #89.

Part of #311 (Group B, installer and update). Owner: not assigned. Task base and PR target: develop. Independent of other sub-issues.

Intended behavior

A user can remove ElastOS on purpose and completely. They choose whether to keep their data, and the documentation lists the real paths on each platform.

Current behavior

• No elastos uninstall command exists, and docs/INSTALL.md has no removal section.
• The installed-files table in docs/INSTALL.md (near lines 350-356) lists only Linux paths (~/.local/share/elastos/...).
• macOS uses ~/Library/Application Support/elastos (scripts/install.sh:318).

Constraints

• The data directory holds identity keys, wallets and recovery material (SECURITY.md, "Stored keys and recovery"). Removing data must be a separate, explicit choice that tells the user to keep their Recovery Kit.
• Stop the Runtime through the same identity-checked control the installer uses (installer_runtime_control), never with a broad pkill.

Done means

• docs/INSTALL.md lists the macOS and Linux paths for binary, data, components and sources. Proof: https://github.com/Elacity/elastos-runtime/blob/aa3d61e4478a1a1a63dbef0dae97c23a0f9f4851/docs/INSTALL.md#L335-L343
• A documented removal path exists: a command (elastos uninstall [--remove-data]) or a documented script. It removes the binary, components and launch entries, and removes data only on request. Test: after removal without --remove-data, a fresh install restores the same identity. After a full removal, no file remains under the listed paths. Proof: https://github.com/Elacity/elastos-runtime/blob/aa3d61e4478a1a1a63dbef0dae97c23a0f9f4851/docs/INSTALL.md#L355 and https://github.com/Elacity/elastos-runtime/blob/aa3d61e4478a1a1a63dbef0dae97c23a0f9f4851/scripts/install-bootstrap-test.py#L1266