`bunx stash impl` requires an interactive TTY for the agent-target picker

[auxesis]

Running bunx stash impl from a non-TTY context (CI, an automation harness, the Claude Code Bash tool, anything piped) hangs
on the prompt:

┌  CipherStash Implementation
│
●  Plan at `.cipherstash/plan.md` — agent will execute it as the source of truth.
│
◆  How would you like to finish setup?
│
└

The picker selects between handoff targets (Claude Code, Codex, AGENTS.md for Cursor/Windsurf/Cline, @cipherstash/wizard).

It only reads from /dev/tty and waits forever.

To reproduce with stash v0.14.1:

echo "" | bunx stash impl   # hangs indefinitely
bunx stash impl < /dev/null # hangs indefinitely

In a real TTY (bunx stash impl directly in a terminal) the picker works fine.

[unitedideas]

The non-TTY case is also where agent harness import tools tend to fail: the caller is often Claude Code, Codex, CI, or a setup script that cannot answer an interactive picker.

A flag shape like this would cover the agent path cleanly:

bunx stash impl --target codex --no-interactive
bunx stash impl --target claude-code --no-interactive
bunx stash impl --target agents-md --no-interactive

It might also be worth failing fast when stdin is not a TTY and no target is supplied. That gives the calling agent a recoverable error instead of a hung subprocess.

We hit the same class of issue in Bring Your AI import-smoke work: the migration path has to be executable from another agent, not only from a human terminal.
https://bringyour.ai/codex-import-smoke