Add agentic coding loop with tools and orchestrator

[cpetersen]

Summary

Adds a Claude Code-style agentic coding assistant to ragnar. The agent can read files, write code, run commands, and self-correct — all orchestrated by a two-level loop architecture designed to be readable and hackable by Ruby developers.

Architecture: Two Levels of Looping

Level 1 — Tool execution (RubyLLM handles this)
The LLM makes tool calls within a single turn. RubyLLM automatically executes tools, feeds results back, and loops until the LLM produces a final response.

Level 2 — Task orchestration (Orchestrator)
The "brain outside the brain" manages multiple LLM turns:

• Auto-detects project type (Ruby/Rust/Node/Python) and runs validation between turns
• Feeds test failures back to the LLM for self-correction
• Uses tool-based signaling for completion detection (not string heuristics)

Tools (8 RubyLLM::Tool subclasses)

Tool	Purpose
ReadFile	Read files with line numbers, offset/limit
WriteFile	Create/overwrite files
EditFile	Search-and-replace with uniqueness validation
BashExec	Shell execution with safety blocklist
ListFiles	Glob-based file search
Grep	ripgrep/grep content search
TaskComplete	Agent signals task completion (uses halt)
AskUser	Agent requests user clarification (uses halt)

Key Design Decisions

• TaskComplete tool instead of string matching — The agent explicitly signals completion by calling a tool, not by saying "I'm done" in prose. RubyLLM's halt mechanism stops the loop immediately. This eliminated a bug where the orchestrator looped 6 times after the agent was already done.
• AskUser tool for user interaction — Same pattern: the agent calls a tool to pause and ask the user, rather than the orchestrator parsing the response for questions.
• Validation is orchestrator-driven — The LLM doesn't decide to run tests; the orchestrator runs them automatically after detecting file changes.

CLI

# Agentic coding mode
ragnar --profile opus code "Write FizzBuzz in Ruby and run it"

# In TUI
ragnar> /code Add error handling to the login form

Files

• lib/ragnar/tools/ — 8 tool classes (~310 lines)
• lib/ragnar/agent.rb — Agent with persistent chat + tools (114 lines)
• lib/ragnar/orchestrator.rb — Level 2 loop (163 lines)
• exe/ragnar — Fixed arg ordering for --profile before command

Test plan

• 387 specs, 0 failures (49 new)
• ragnar --profile opus code "Create fizzbuzz.rb in /tmp and run it" — completes in 1 iteration
• Tool calls display in real time
• Existing RAG, TUI, profile features unaffected
• BashExec blocks dangerous commands (rm -rf /, shutdown)
• EditFile rejects ambiguous matches
• TaskComplete/AskUser use RubyLLM halt correctly

🤖 Generated with Claude Code