feat: interactive picker when cloak switch is run with no name

[thekvn]

What

cloak switch (and its use alias) used to error when called without an argument. Now it shows an interactive list of your cloaks and lets you pick one — the current cloak is marked (current).

$ cloak switch
? Which cloak do you want to wear? (Use arrow keys)
❯ home
  work (current)

Why it's safe under shell integration

The shell wrapper runs command cloak switch --print-env, capturing stdout for eval. So the picker UI is rendered to stderr (via inquirer's output option); stdout still receives only the export CLAUDE_CONFIG_DIR=... line. Verified manually that stdout stays clean while the menu shows on the terminal.

Edge cases handled:

• Abort (Ctrl-C / EOF): exits cleanly with empty stdout and no stack trace, so the shell eval "" is a harmless no-op.
• No cloaks saved: exits 1 with a friendly "create one" hint.
• Picking the cloak you're already wearing: same as before — message to stderr, nothing to eval.

Changes

• src/commands/switch.js — picker path (injectable via options.pickChoice, matching the existing setupChoice test seam)
• src/cli.js — switch <name> → switch [name]
• src/lib/messages.js — switchPick prompt
• Docs: README.md, CLAUDE.md

Tests

Added to tests/switch.test.js (all existing cases still pass):

• S-11 — no name + selection switches to the chosen cloak (emits its export)
• S-12 — no name with no cloaks exits 1 and writes nothing to stdout
• S-13 — picking the active cloak produces no stdout

Full suite green.

🤖 Generated with Claude Code