feat: pos ai hf — Hugging Face model downloader for local inference

Bash-native tool using curl/jq to download AI models from HF Hub.
Subcommands: download (single file/repo/gguf filter), search, list, remove.
Auth via HF_TOKEN in ai.env, resume support, disk space pre-flight,
rate limit handling, .hf-meta metadata tracking.

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

completions/pos.bash

@@ -3,6 +3,7 @@
 # Install: source this file in ~/.bashrc or place in /etc/bash_completion.d/
 # GEN:START posflags
 declare -A _pos_flags
+_pos_flags[ai-hf]="--branch --gguf --output"
 _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"
@@ -44,7 +45,7 @@ _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 openrouter"
+_pos_subcmds[ai]="ask chat sessions capture models providers alias gemini hf openrouter"
 # GEN:END possubcmds
 # GEN:START posconfigscopes
 declare -a _pos_config_scopes=(ai compose entertainment grab matrix notify scrcpy system telegram ytsync)