docs: Replace cloning with a fresh-Tails handoff workflow #213

Problem

The README promotes cloning, but the current clone command is unfinished. A full-device copy is also the wrong abstraction for selective handoff: it either transfers all encrypted persistent state, potentially including wallet ciphertext and metadata, or gives the recipient no choice about what is copied.

Issue #42 covers hiding the broken Backup/Clone menu actions. This issue defines the replacement distribution model.

Selected approach

Document a fresh-Tails, user-controlled handoff:

• Create or clone the destination using normal Tails procedures rather than treating the Tails Cloner as a selective-backup tool.
• Let the recipient create and unlock their own Persistent Storage.
• Transfer an authenticated CipherStick .tar or .zip release and extract it onto the unlocked destination.
• Let the person performing the handoff explicitly choose any additional data to copy, such as selected Bitcoin Core blockchain data.
• Do not let CipherStick silently decide whether wallet ciphertext, keys, configuration, logs, or other persistent state is included.
• Clearly identify source, destination, selected paths, and consequences before any optional transfer.

The first deliverable may be documentation. Any later transfer helper should be proposed and reviewed separately.

Dependencies

• Clicking Backup or Clone in the menu may break the installation #42 removes the unfinished menu action.
• Authenticate CipherStick releases before update #206 provides an authenticated CipherStick release package suitable for handoff.

Acceptance criteria

• Supported documentation no longer describes the unfinished command or a full persistent-state copy as the normal clone workflow.
• Installation, CipherStick package transfer, and optional data transfer are separate documented steps.
• Every optional copied path is an explicit user decision.
• Documentation warns when selected data may contain wallet material or identifying state.
• The CipherStick archive is authenticated before execution.
• No privacy, censorship-resistance, or trust claim depends on inheriting another person's Tails state.