repo: remove superseded pilot files, ASCII-clean the build and nginx configs

Drops the legacy course-1 template, the two python assemblers the node
assembler replaced, and the unversioned scene manifest left over from the
manifest-<type> split - none referenced by build.sh, the assembler or the
README, and none produce build output. The v2 pages stay: the README lists
them as parked. Also converts typographic dashes to ASCII in build.sh and the
two nginx configs, and corrects an assembler comment that still pointed at the
removed python build.

pilot/assemble-arc.mjs

@@ -3,7 +3,7 @@
 // Reads pilot/arc.tpl.html, splits the app <script> out to a fingerprinted arc.js, injects
 // the scene manifests, fingerprints every /assets/ file, sets intrinsic image dimensions,
 // wraps a full HTML document, writes build.json, and runs preflight gates.
-// Runs on bare node (the build image has no python). Artifact build = assemble-arc.py.
+// Runs on bare node (the build image has no python). Superseded the earlier python assembler.
 import { readFileSync, writeFileSync, mkdirSync } from "node:fs";
 import { createHash } from "node:crypto";
 import { dirname, join } from "node:path";