fix: pos config ai splits llamacpp into its own section

LLAMACPP_* keys lived under a generic General group. Added a conditional
'@[AI_PROVIDER=llamacpp] llamacpp' caption (mirrors OpenRouter), so the
provider gets its own section; General now only holds AI_SYSTEM_PROMPT
plus the HF keys that arrive from pos-ai-hf. AI_PROVIDER description and
usage text mention llamacpp.

Also: inactive config groups no longer dim the key name — keys stay bold
so an inactive provider block is not one uniform grey wall; only values
and descriptions dim, and the caption still carries the inactive reason.

DOC/AGENT_Context_Project.md

@@ -652,7 +652,7 @@ Use conventional prefixes: `feat:`, `fix:`, `docs:`, `refactor:`, `chore:`
 | `bin/pos-system-health` | 209 | Host health dashboard (disk, RAM, services, backup age, fail2ban, docker); exit 1 if any FAIL |
 | `bin/pos-system-schedule` | 151 | Scheduled jobs: run a command on a timer; notify on threshold/change/error/always or silently |
 | `bin/pos-system-uninstall` | 435 | Remove pos toolkit binaries, services, shell integration, config, and data |
-| `bin/pos-ai` | 696 | AI assistant: ask, chat, sessions, capture, models, providers |
+| `bin/pos-ai` | 702 | AI assistant: ask, chat, sessions, capture, models, providers |
 | `bin/pos-config` | 80 | Interactive editor for the tools' runtime config (reads # POS_CONFIG: registry) |
 | `bin/pos-tree` | 118 | Show the pos CLI command tree: categories, commands, and subcommands |
 | `completions/pos.bash` | 312 | Dynamic bash completion |