Add registry sort/pagination features and improve code step dialog

Registry:
- Add owner and rating sort options to both server endpoints
- Add letter-based prefix filtering (A-Z, #) with server-side validation
- LEFT JOIN tool_stats for average_rating/rating_count in responses
- Add interactive numbered page buttons with sliding window and ellipsis
- Add letter bar UI (shown when sorting by name) with highlight state
- Auto-select asc/desc order based on sort field
- Disable cell editing on results table
- Client: add order and prefix params to list_tools/search_tools

Code step dialog:
- Split AI prompt into user instruction input and collapsible wrapper
- User types plain instruction, wrapper is hidden by default
- Injection of user text into wrapper via {user_instruction} placeholder
- Increase dialog minimum height to 750px

Runner:
- Support variable substitution in prompt step provider name

Co-Authored-By: Claude Opus 4.5 <[email protected]>

src/cmdforge/runner.py

@@ -209,8 +209,8 @@ def execute_prompt_step(
             # Prepend system prompt to user prompt
             prompt = f"{profile.system_prompt}\n\n---\n\n{prompt}"
 
-    # Call provider
-    provider = provider_override or step.provider
+    # Call provider (support variable substitution in provider name, e.g. {settings.provider})
+    provider = provider_override or substitute_variables(step.provider, variables, warn_non_scalar=verbose)
 
     if provider.lower() == "mock":
         result = mock_provider(prompt)