Land prototype on main (fix stacked-PR retarget gap)

PRs #10 and #11 were merged into their intermediate base branches
(restructure/working-copy-root and proto-improvements) rather than main,
because the stacked PRs' bases were not auto-retargeted (the branches were
not deleted on merge). As a result main only received the #9 restructure
and is still the plain working-copy bot.

This brings the full prototype onto main as a clean delta on top of the
current main tree (identical content to proto-improvements, but with main
ancestry so it merges without the squash-induced rename/delete conflicts):

- constants.py: env-var config, safe JSON loading, dependency guards,
  env->netrc tokens, API_SHARED_KEY + service_headers(), CONAN_* config
- communication_subroutine.py: queue timeout/Empty, daemon threads,
  cooperative stop_event, inbound _authorize_request()
- bot.py: asyncio event loop + load conanjurer_commands
- music_functions / radio_commands / librarian_commands: X-Conjurer-Api-Key
- conanjurer_commands/_functions: fixed + integrated bridge with RCON
  player-join notifications
- requirements_bot.txt: aiomcrcon, asyncssh
- conjurer_musician/.gitignore: keep runtime playlists/mp3 out of the repo

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

librarian_commands.py

@@ -15,7 +15,9 @@ from discord.ext import commands, tasks
 
 from ai_functions import handle_response
 from communication_subroutine import IN_COMM_Q, OUT_COMM_Q, QueryControl
-from constants import DIR_PATH_SADOX, LIBRARIAN_SERVICE_ADDRESS, SEND_QUERY
+from constants import DIR_PATH_SADOX, LIBRARIAN_SERVICE_ADDRESS, SEND_QUERY, service_headers
+
+SERVICE_HEADERS = service_headers()
 
 
 class DataModule(commands.Cog):
@@ -165,6 +167,7 @@ class DataModule(commands.Cog):
             requests.post,
             f"{LIBRARIAN_SERVICE_ADDRESS}{SEND_QUERY}",
             json=json_query,
+            headers=SERVICE_HEADERS,
             timeout=360,
         )
         await ctx.send(
@@ -260,6 +263,7 @@ class DataModule(commands.Cog):
             requests.post,
             f"{LIBRARIAN_SERVICE_ADDRESS}{SEND_QUERY}",
             json=json_query,
+            headers=SERVICE_HEADERS,
             timeout=360,
         )
         await ctx.send(