feat(builder): documented launch options only, and no game-specific code

Launch options must be documented. A draft passed an option its server
doesn't have; servers ignore unknown options, so it booted and passed every
boot test while its setting did nothing. build now reads the pages research
based the variant on, in full, and the drafter rejects any launch option in
the startup command that none of them, nor the image's own scripts, mention.
Shell tools' options (mkdir -p, [ -n ...]) are skipped; the check is off
without sources.

The builder is game-agnostic:
- AUTHORING.md (the model's rules), the research prompt and the schema
  describe the rules without naming a game.
- The draft prompt no longer includes real templates from the repo. Its
  format example is one invented server (no real command, options, ports or
  app id), checked by TestExampleTemplateFollowsTheRules.
- Comments, help texts, BUILDER.md and test fixtures use invented names and
  values.
- TestBuilderIsGameAgnostic reads every game's name and id from games/ and
  fails if any appears in the builder's code, tests, rules, schemas or docs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

BUILDER.md

@@ -25,12 +25,17 @@ progress / log / variants        ◄─post── build: first boot → draft
    validates but never booted still gets a PR, titled `WIP:`, with what's left listed. Nothing reaches
    players until a person merges it and enables the game.
 
+The builder is **game-agnostic**: everything about a game comes from that game's research, first boot and
+boot tests. No game's name, id or code may appear in the builder's source, its rules for the model
+(`AUTHORING.md`), the schemas or this file, and the model is never shown another game's template (its format
+example is an invented server). `TestBuilderIsGameAgnostic` fails the build if one does.
+
 The worker only connects out (to the panel, Gitea, the model and the search services).
 
 ## Requirements
 
 A Docker host with the isolated `gbr-boottest` network (`RUNNER.md`, step 1), so servers booted by the
-builder can't reach private networks. Enough memory for the largest server it builds (~16 GB for ARK) and
+builder can't reach private networks. Enough memory for the largest server it builds (the biggest need ~16 GB) and
 disk for SteamCMD downloads. The image `gbr-builder:latest` is published by
 `.gitea/workflows/builder-image.yml` whenever `cmd/` changes on main.
 
@@ -54,9 +59,9 @@ On any machine with Docker and the `gbr-boottest` network, with `OLLAMA_URL`, `S
 `READER_URL` set:
 
 ```bash
-go run ./cmd/gbrgames research -name Valheim -out research.json
+go run ./cmd/gbrgames research -name "<game>" -out research.json
 # pick a variant from research.json into v.json, then:
-go run ./cmd/gbrgames build -name Valheim -variant @v.json -out build.json
+go run ./cmd/gbrgames build -name "<game>" -variant @v.json -out build.json
 ```
 
 The draft lands in `games/<id>/`, first-boot reports in `firstboot-out/`.