Add AI persona profiles for prompt injection

Profiles allow users to inject system instructions into prompts,
customizing the AI's behavior and persona for tool execution.

Features:
- Profile dataclass with name, description, system_prompt
- 8 built-in profiles: None, Comedian, Technical Writer, Teacher,
  Concise, Creative, Code Reviewer, Analyst
- Custom profile creation and storage in ~/.cmdforge/profiles/
- Profile selector in Prompt Step dialog
- Profile injection during tool execution
- Profiles page in GUI (Ctrl+4) for viewing and managing profiles

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

src/cmdforge/runner.py

@@ -9,6 +9,7 @@ from .tool import Tool, PromptStep, CodeStep, ToolStep
 from .providers import call_provider, mock_provider
 from .resolver import resolve_tool, ToolNotFoundError, ToolSpec
 from .manifest import load_manifest
+from .profiles import load_profile
 
 # Maximum recursion depth for nested tool calls
 MAX_TOOL_DEPTH = 10
@@ -114,6 +115,13 @@ def execute_prompt_step(step: PromptStep, variables: dict, provider_override: st
     # Build prompt with variable substitution
     prompt = substitute_variables(step.prompt, variables)
 
+    # Inject profile system prompt if specified
+    if step.profile:
+        profile = load_profile(step.profile)
+        if profile and profile.system_prompt:
+            # Prepend system prompt to user prompt
+            prompt = f"{profile.system_prompt}\n\n---\n\n{prompt}"
+
     # Call provider
     provider = provider_override or step.provider