feat: serve the one-line installer from the site

The site serves install.sh at /retrobios/i and install.ps1 at
/retrobios/i.ps1. generate_site.py writes both copies with the
installer address set to install.py at the commit the site is built
from (GITHUB_SHA in CI, HEAD locally), so the pinned SHA-256 and the
downloaded installer always come from one commit, including while a
deploy is still running.

Every command a user copies names the short address. The raw form
stays on the installer page as the fallback. Deploy Site now runs on
changes to install.sh and install.ps1. The install box weight keeps
the address length its ratio was fitted on, so no console page moves.

scripts/siteguides.py

@@ -18,6 +18,7 @@ from pathlib import Path
 
 import sitemarkup as markup
 from safeparse import require_yaml
+from sitebootstrap import PS1_NAME, SH_NAME
 
 PLATFORMS_DIR = Path(__file__).resolve().parent.parent / "platforms"
 GUIDES_FILE = PLATFORMS_DIR / "_guides.yml"
@@ -380,6 +381,9 @@ def load_guides(path: Path = GUIDES_FILE, registry: dict | None = None) -> dict:
 
 _LOADED = load_guides()
 INSTALL_BASE: str = _LOADED["install_base"]
+# The bootstraps the site serves (sitebootstrap.py writes them).
+INSTALL_SH: str = f"{INSTALL_BASE}/{SH_NAME}"
+INSTALL_PS1: str = f"{INSTALL_BASE}/{PS1_NAME}"
 DEVICE_GROUPS: dict[str, tuple[str, str]] = _LOADED["device_groups"]
 GROUP_ANCHORS: dict[str, str] = _LOADED["group_anchors"]
 ALSO_RUNS: dict[str, tuple[tuple[str, str, str, str, str], ...]] = _LOADED["also_runs"]
@@ -435,10 +439,10 @@ def install_command(shell: str, args: str = "") -> str:
     takes none.
     """
     if shell == "sh":
-        return f"curl -fsSL {INSTALL_BASE}/install.sh | sh" + (f" -s -- {args}" if args else "")
+        return f"curl -fsSL {INSTALL_SH} | sh" + (f" -s -- {args}" if args else "")
     if args:
-        return f"&([scriptblock]::Create((irm {INSTALL_BASE}/install.ps1))) {args}"
-    return f"irm {INSTALL_BASE}/install.ps1 | iex"
+        return f"&([scriptblock]::Create((irm {INSTALL_PS1}))) {args}"
+    return f"irm {INSTALL_PS1} | iex"
 
 
 # The title over each command block, by the shell it is written for.