Provide a portable Linux x86_64 Sahara artifact

[nidheesh-p]

Goal

Offer a documented Linux installation that does not require a system Python while keeping the initial compatibility promise narrow.

Scope

• Build a portable Linux x86_64 archive from the standalone runtime.
• Define the supported libc and distribution baseline.
• Include an install script or documented symlink step that does not modify system Python.
• Verify semantic search, sqlite-vec, ONNX Runtime, keyring fallback, and stdio MCP behavior.
• Publish a checksum and bundled-dependency inventory.

Acceptance Criteria

• The artifact works on the documented clean Linux targets without Git, pip, pipx, or a system Sahara installation.
• sahara --version, setup, index, search, and stdio MCP succeed.
• Unsupported architectures and distributions are stated clearly.
• Upgrade and removal preserve user data by default.
• The build runs only manually or for releases.

Dependencies

Follow the stable standalone-runtime and native-release workflow patterns.

See specs/SIMPLE_INSTALLER_PLAN.md.