Feat/self critic coaching

[yhyu13]

Summary

This PR introduces three built-in agent skills — Critic, Replacer, and Toolcoach — that work together as a middleware stack around the primary SessionAgent. The goal is to improve output quality, prevent regressions, and coach the agent toward better tool usage patterns without adding perceivable latency.

What Changed

1. Critic Skill (internal/skills/critic/)

A secondary-LLM review layer that inspects the agent's diff after each turn and returns one of:

• approve — changes look good, turn completes normally
• revise — rollback changes, inject feedback, re-drive the primary agent
• halt — rollback changes, return error to user

Key features:

• SQLite-backed review persistence with sqlc-generated queries
• SHA-256 keyed LRU cache for deduplicated reviews
• Circuit breaker + timeout for resilient LLM calls
• LSP diagnostic fetching for richer context
• Configurable via crush.json (options.critic)
• CLI commands: crush critic list, crush critic show, crush critic stats
• Per-session disable via ReplacerEnabled flag

2. Replacer Skill (internal/skills/replacer/)

A conversation coach that evaluates whether the primary agent's response is complete or needs a follow-up. Uses a small/fast model to decide stop vs continue.

Key features:

• Configurable max iterations (default 3)
• Duplicate-prompt guard to avoid repetitive follow-ups
• Timeout handling (deadline exceeded = treat as stop)
• Coach spinner indicators ("Coach is ready" → "Coach is evaluating")
• /skipcoach command to interrupt current evaluation one-time
• Commands dialog integration ("Skip Coach")
• Auto-interrupt on user typing or Enter press

3. Toolcoach Skill (internal/skills/toolcoach/)

A zero-LLM, heuristic-based skill that detects anti-patterns in real-time tool usage and injects coaching tips into tool results.

Key features:

• ~2.7µs overhead per tool call (benchmarked)
• Detects patterns: destructive_bash, write_over_existing, edit_without_view, broad_grep, repeated_view, missing_multiedit
• SQLite effectiveness tracking with adaptive severity
• Progressive coaching (hint → warning → critical) based on repetition
• Guided retry mechanism for destructive operations
• Configurable via crush.json (options.toolcoach)

4. Middleware Stack Order

outermost: ToolcoachMiddleware
            ↓ wraps
           ReplacerMiddleware
            ↓ wraps
           CriticMiddleware
            ↓ wraps
inner-most: SessionAgent (primary)

SkipCoach propagates through the chain via interface type-assertion at each layer.

5. UI & Integration

• New commands dialog items: "Skip Coach"
• /skipcoach (or skipcoach) intercepted in textarea
• AgentSkipCoach(sessionID) wired through workspace → coordinator → middleware chain
• Coach evaluation no longer blocks user commands (typing, new session, model selection, etc.)
• Visual busy indicators preserved (placeholder, progress bar, cancel key, todo spinner)

6. Database & Schema

New migrations:

• critic_reviews table (verdict, confidence, concerns, diff snapshot)
• written_files table (tracks files written per session for diff baseline)
• toolcoach_effectiveness table (pattern hit/miss tracking)

Testing

# Critic tests
go test ./internal/skills/critic/... -v -race

# Replacer tests
go test ./internal/skills/replacer/... -v -race

# Toolcoach tests
go test ./internal/skills/toolcoach/... -v -race

# Standalone critic + replacer demo (no API keys)
go run ./cmd/critic-demo

Configuration Example

{
  "options": {
    "critic": {
      "enabled": true,
      "model": "anthropic/claude-sonnet-4",
      "max_iterations": 3,
      "auto_approve": false,
      "threshold": 0.85
    },
    "replacer": {
      "enabled": true,
      "max_iterations": 3
    },
    "toolcoach": {
      "enabled": true,
      "max_patterns": 100
    }
  }
}

Checklist

• I have read CONTRIBUTING.md.
• I have created a discussion that was approved by a maintainer (for new features).

[charmcli]

All contributors have signed the CLA ✍️ ✅
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[yhyu13]

I have read the Contributor License Agreement (CLA) and hereby sign the CLA.