feat(builder): launch options must appear in the research sources

The Valheim draft in #13 passed -maxplayers, an option Valheim doesn't have.
The server ignores unknown options, so the draft booted and passed every
boot test while its MaxPlayers 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. The model gets it back to remove or
spell correctly. Options of shell tools (mkdir -p, [ -n ...]) are skipped.
The check is off when there are no sources (draft run by hand, no reader).

Against #13's 11 real sources it flags -maxplayers and nothing else.

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

AUTHORING.md

@@ -54,6 +54,8 @@ Know this before writing anything:
 - Read settings under the names the agent gives them (see above). `${RCON_PORT}` when the setting is
   `RCONPort` silently ignores the owner's value; it arrives as `RCONPORT`.
 - Use `${VAR:-default}` for anything that may be unset.
+- Only use launch options the game's documentation lists, spelled as it spells them. Servers ignore options
+  they don't know, so an invented one (`-maxplayers` for Valheim) boots fine and its setting does nothing.
 - Quote text settings where they're used: `-name "${SERVER_NAME}"`. `ARGS="-name ${SERVER_NAME}"; ./server $ARGS`
   splits "GBRHosting - My Server" into words; build optional arguments in a bash array instead
   (`args=(-name "$SERVER_NAME"); [ -n "$PASSWORD" ] && args+=(-password "$PASSWORD"); ./server "${args[@]}"`).