Merge vllmScripts under llm/ (history-preserving import)

The vllmScripts repository (LLM inference fleet: serve scripts, systemd
units, env tunables, deployment runbook, research docs) is merged into
this repository. Its full history is grafted under llm/ with a
two-parent merge commit so no commit is lost.

A follow-up commit reorganizes llm/ into the repo layout:
llm/docs -> docs/LLM, llm/scripts -> scripts, llm/old -> old.

llm/.gitignore

@@ -0,0 +1,6 @@
+.pi-subagents/
+.AGENTTRASH/
+__pycache__/
+*.pyc
+.venv/
+.obsidian/