feat: pos ai server — llama.cpp local inference server

Service manager (start/stop/status/models/logs) with systemd user
service generation, GPU auto-detection, model selection from pos ai hf
downloads. Provider adapter integrates with pos ai ask as --provider
llamacpp. Config extends existing ai scope with LLAMACPP_* keys.

87 test cases / 0 failed. make gen/check/lint 0 FAIL / 0 WARN.

completions/pos.bash

@@ -4,6 +4,7 @@
 # GEN:START posflags
 declare -A _pos_flags
 _pos_flags[ai-hf]="--branch --gguf --output"
+_pos_flags[ai-server]="--port --host --model --ctx --gpu --threads"
 _pos_flags[communication-matrix-listener]="--enable --disable --status --run"
 _pos_flags[communication-telegram-listener]="--enable --disable --status --sync-commands --run"
 _pos_flags[communication-telegram-sender]="--type --caption --parse-mode --no-preview --token --chat-id --markdown"
@@ -30,6 +31,7 @@ declare -A _pos_subcmds
 _pos_subcmds[ai-alias]="create edit remove list show"
 _pos_subcmds[ai-gemini]="ask chat models sessions capture"
 _pos_subcmds[ai-openrouter]="ask chat sessions capture"
+_pos_subcmds[ai-server]="start stop status models logs"
 _pos_subcmds[communication-matrix-sender]="send test login"
 _pos_subcmds[communication-scrcpy]="devices record tcpip connect push pull screenshot info"
 _pos_subcmds[communication-telegram-listener]="prefix"
@@ -45,7 +47,7 @@ _pos_subcmds[share-smb-client]="mount unmount list persist unpersist menu"
 _pos_subcmds[share-smb-server]="status share unshare list adduser deluser reload enable disable menu"
 _pos_subcmds[system-backup]="menu"
 _pos_subcmds[system-schedule]="run list config enable disable status migrate menu"
-_pos_subcmds[ai]="ask chat sessions capture models providers alias gemini hf openrouter"
+_pos_subcmds[ai]="ask chat sessions capture models providers alias gemini hf openrouter server"
 # GEN:END possubcmds
 # GEN:START posconfigscopes
 declare -a _pos_config_scopes=(ai compose entertainment grab matrix notify scrcpy system telegram ytsync)