feat(cli): `collie pack join bluefin` is a whole command

Joining a pack asked the operator for four things they had no way to know: the
lead's full MagicDNS name, its port, `--insecure` for a scheme they never typed,
and a token pasted through stdin. Every one of them has a sane default, and each
default is still overridable by the flag or the spelling that always won.

- An address with no scheme and no port now means `https://<host>:8787`. 8787 is
  the port a Collie binds, so it is the only thing a bare host can mean. A typed
  port or a typed scheme is taken as typed, so no existing spelling moves.
- A lead that answers 8787 over plain HTTP fails the handshake, not the request.
  `join` recognises the shapes that failure takes (probed against Bun 1.4's
  fetch, plus the OpenSSL spellings every other runtime produces), asks once in a
  terminal whether to send the token over plain HTTP, and retries only on `y`.
  The question comes BEFORE the token is sent. No terminal, or any other answer,
  keeps exactly the refusal that shipped; an address spelled `http://` by hand
  still requires `--insecure` and is never asked about, so no script changes
  meaning.
- No token argument, in a terminal, asks for one. The answer skips the `ps`
  warning on purpose: it was never in argv.
- `--label` defaults to this machine's hostname, so a peer is named after its box
  instead of `collie-8f3a2b1c`.
- The lead's stored address is now the origin that ANSWERED, not the string that
  was typed. A peer re-dials its lead on every poll, and a bare `bluefin` would
  have sent all of those to :443.
- `pack invite` leads with `collie pack join <short-name>` and keeps the stdin
  form under it. The port is appended only when this lead moved off 8787.

`pack join` and `pack leave` become the canonical spellings — every other pack
verb is a `pack` sub-verb, and these two were the exception for no stated reason.
`collie join` and `collie leave` stay as aliases onto the same two functions, so
1.0.0 docs and scripts keep working; a test pins that the two spellings are one
code path.

Also: the pointer to DEPLOYMENT.md becomes docs/deployment.md (7fe89b7).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>