v3.0.0

AI generated. Reviewed by Johnny.

This release makes jd a standalone program, and removes the 1.x shims.

Breaking changes

• The jd-nav/ and jd-prompt/ directories are gone. A .zshrc that
  sources either one now fails at shell start with "no such file".
  Replace that line with source ~/.jd/cli/jd.sh.
• jd new --json no longer changes directory. It prints the object and
  exits. Without --json, jd new moves into the new folder as before.

Features

• bin/jd is the program. It can be run without sourcing anything,
  from a script, cron, an agent, or another program.
• A move run from the program prints the folder on stdout and exits 0,
  so cd "$(~/.jd/cli/bin/jd 11.11)" works.
• The shell hook sets JD_HOOK when it runs the program. A move then
  exits 3 instead of 0, and the hook does the cd.
• --system is now read only as the first word, so it cannot be taken
  for a title or for a flag of jd new.
• jd help now works without a config.
• source ~/.jd/cli/jd.sh now adds ~/.jd/cli/bin to $PATH.

Changes

• jd.sh is now a hook. It defines jd, jdex and one command per
  system, adds bin to $PATH, and loads nothing from lib but the
  zsh prompt. Each function it defines is self-contained, so a shell
  that copies jd without its helpers still gets a working command.
• The version number now lives only in bin/jd. jd version reads it
  from there.
• jd and jdex no longer hard-code a system. The program resolves
  the default on every run, so a config edit takes effect immediately.