move host setup into scripts/setup/

scripts/ was holding two unrelated kinds of thing: install-this-machine, and run-this-occasionally. The
eight installers now live in scripts/setup/; what stays at the top level is the build steps (gen-index,
prebuild, build/) and the two maintenance scripts (reindex-music, rebuild-soulseek-tree).

The move is not just a rename. Three of these derive the repo root from their own location:

  setup.sh:51            PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
  setup_mac_light.sh:51  same
  cleanup-desktop.sh:134 ENV_FILE="$(dirname "$0")/../.env"

Left alone, all three would now resolve to scripts/ — and nothing downstream complains. PROJECT_DIR is
where .env is written, where `bun install`, `gen:index` and `db:push` run, and what pm2 is pointed at, so
a fresh install would have quietly provisioned scripts/ and reported success. cleanup-desktop.sh fails
the other way: it would find no .env, print "No .env — skipping", and leave the real VNC_PASSWORD in the
real file. All three are now `../..` with a comment saying why the level matters.

provision-user-dirs.ts imports data-path.ts relatively; that one tsgo caught.

Also disambiguated `setup.sh` where it had become two files. app-store/templates/<name>/setup.sh is a
per-sidecar installer with its own contract, and preflight.ts + docs/sidecar-app-store.md discussed both
in the same paragraph. The host one is now spelled with its full path at those sites.

Verified: bash -n on all six shell scripts, tsgo clean, os-user tests pass, both derivations resolve to
the repo root, starship.toml still resolves from os-user-shell.ts, and provision-user-dirs.ts runs under
DRY_RUN.

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

scripts/setup/starship.toml

@@ -0,0 +1,45 @@
+add_newline = true
+command_timeout = 200
+format = """
+$username$hostname:[$directory$git_branch$git_status]($style)
+$character"""
+
+[username]
+format = "[$user]($style)@"
+style_user = "bold green"
+show_always = true
+
+[hostname]
+format = "[$hostname]($style)"
+style = "bold yellow"
+ssh_only = false
+
+[character]
+error_symbol = "[✗](bold #61afef)"
+success_symbol = "[❯](bold #61afef)"
+
+[directory]
+home_symbol = "~"
+truncation_length = 0
+truncate_to_repo = false
+
+[git_branch]
+format = " [$branch]($style) "
+style = "italic #61afef"
+
+
+[git_status]
+format     = '[$all_status]($style)'
+style      = "#61afef"
+ahead      = "⇡${count} "
+diverged   = "⇕⇡${ahead_count}⇣${behind_count} "
+behind     = "⇣${count} "
+conflicted = " "
+up_to_date = " "
+untracked  = "? "
+modified   = " "
+stashed    = ""
+staged     = ""
+renamed    = ""
+deleted    = ""
+