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>

src/servers/os-user-claude.ts

@@ -8,7 +8,7 @@ import { osUserHome, runAs } from './os-user';
 // A single `/usr/local/bin/claude` would be less disk and one version to reason about, and the argument for
 // it is real: the private part of Claude is the credential in `~/.claude`, not the executable. It is still
 // the wrong shape here. `claude` updates itself — that is why the owner's own install goes through
-// Anthropic's installer rather than npm (`scripts/setup.sh:853`) — and a root-owned binary is one a member
+// Anthropic's installer rather than npm (`scripts/setup/setup.sh:861`) — and a root-owned binary is one a member
 // cannot update, which turns "my agent is a version behind" into a request to the owner. Per-member also
 // means the account's agent keeps working exactly as the tool ships, with no platform-shaped exception to
 // explain. Same command the owner ran, run as them, in their home.
@@ -29,7 +29,7 @@ import { osUserHome, runAs } from './os-user';
 // report whether the credential has appeared, so the UI can render the one-line instruction instead of an
 // agent that fails for reasons nobody can see.
 
-/** Anthropic's own installer — the same one `scripts/setup.sh` uses for the owner, chosen for auto-update. */
+/** Anthropic's own installer — the same one `scripts/setup/setup.sh` uses for the owner, chosen for auto-update. */
 const CLAUDE_INSTALL_URL = 'https://claude.ai/install.sh';
 
 /**