feat: add permission modes and CLI orchestration layer

Permission Modes:
- Add default/plan/auto_accept modes controlling tool access
- Plan mode restricts Task agent to read-only tools only
- Auto-accept mode bypasses approval prompts (with confirmation)

Approval Scaffolding:
- Add ApprovalRule/ApprovalRuleSet for granular tool control
- Pattern-based matching on tool name and arguments
- Default rules for common safe/dangerous patterns
- Prep for future bidirectional approval flow

CLI Refactor:
- Default to Task agent (main orchestrator)
- Add --mode flag and runtime mode switching
- Integrate prompt_toolkit for better UX:
  - Persistent command history (~/.webber_history)
  - Tab completion for commands and file paths
  - Auto-suggest from history
- Deprecate standalone 'explore' command

Other:
- Split CHANGELOG.md into per-package files
- Update AGENTS.md release procedure for both packages

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

webber-api/src/domains/agents/task/prompts.py

@@ -3,10 +3,68 @@ System prompts for the Task agent.
 
 The Task agent is a full orchestrator that can:
 - Execute multi-step tasks autonomously
-- Use all tools (read + write)
+- Use all tools (read + write) based on permission mode
 - Spawn sub-agents (Explore, Plan) for focused work
 """
 
+TASK_PLAN_MODE_PROMPT = """You are a codebase analysis and planning agent in READ-ONLY mode.
+
+You can explore and analyze code but CANNOT modify files or execute write operations.
+
+AVAILABLE TOOLS (read-only):
+
+File Operations:
+- read_file: Read file contents with line numbers
+- glob_files: Find files by pattern
+- grep_content: Search file contents with regex
+
+Shell:
+- bash_readonly: Read-only commands (ls, git status, git log, git diff, etc.)
+
+Orchestration:
+- spawn_agent: Launch sub-agents for focused tasks (explore, plan only)
+
+WORKFLOW:
+1. Understand the request
+2. Explore the codebase to gather context
+3. Analyze code structure and patterns
+4. Create detailed implementation plans
+5. Return findings with actionable recommendations
+
+TOOL CALL EXAMPLES:
+
+To find all Python files:
+  Call glob_files with pattern="**/*.py"
+
+To search for a function:
+  Call grep_content with pattern="def my_function"
+
+To check git status:
+  Call bash_readonly with command="git status"
+
+To get deeper analysis:
+  Call spawn_agent with agent_type="explore" and prompt="find authentication code"
+
+RULES:
+- ALWAYS use tools first, then analyze results
+- Never guess file contents - read them first
+- Be thorough in exploration
+- Provide specific file paths and line numbers in findings
+
+OUTPUT FORMAT:
+Structure your response with:
+
+### Analysis
+- What was found
+- Key patterns identified
+- Relevant files
+
+### Recommendations
+- Suggested approach
+- Potential concerns
+- Next steps (to be executed in full mode)
+"""
+
 TASK_SYSTEM_PROMPT = """You are an autonomous task execution agent.
 
 You have access to ALL tools including file editing, writing, and bash execution.