feat: complete OpenCode plugin support with hooks, tools, and commands

Major OpenCode integration overhaul:

- llms.txt: Comprehensive OpenCode documentation for LLMs (642 lines)
- .opencode/plugins/ecc-hooks.ts: All Claude Code hooks translated to OpenCode's plugin system
- .opencode/tools/*.ts: 3 custom tools (run-tests, check-coverage, security-audit)
- .opencode/commands/*.md: All 24 commands in OpenCode format
- .opencode/package.json: npm package structure for opencode-ecc
- .opencode/index.ts: Main plugin entry point

- Delete incorrect LIMITATIONS.md (hooks ARE supported via plugins)
- Rewrite MIGRATION.md with correct hook event mapping
- Update README.md OpenCode section to show full feature parity

OpenCode has 20+ events vs Claude Code's 3 phases:
- PreToolUse → tool.execute.before
- PostToolUse → tool.execute.after
- Stop → session.idle
- SessionStart → session.created
- SessionEnd → session.deleted
- Plus: file.edited, file.watcher.updated, permission.asked, todo.updated

- 12 agents: Full parity
- 24 commands: Full parity (+1 from original 23)
- 16 skills: Full parity
- Hooks: OpenCode has MORE (20+ events vs 3 phases)
- Custom Tools: 3 native OpenCode tools

The OpenCode configuration can now be:
1. Used directly: cd everything-claude-code && opencode
2. Installed via npm: npm install opencode-ecc

.opencode/commands/plan.md

@@ -0,0 +1,49 @@
+---
+description: Create implementation plan with risk assessment
+agent: planner
+subtask: true
+---
+
+# Plan Command
+
+Create a detailed implementation plan for: $ARGUMENTS
+
+## Your Task
+
+1. **Restate Requirements** - Clarify what needs to be built
+2. **Identify Risks** - Surface potential issues, blockers, and dependencies
+3. **Create Step Plan** - Break down implementation into phases
+4. **Wait for Confirmation** - MUST receive user approval before proceeding
+
+## Output Format
+
+### Requirements Restatement
+[Clear, concise restatement of what will be built]
+
+### Implementation Phases
+[Phase 1: Description]
+- Step 1.1
+- Step 1.2
+...
+
+[Phase 2: Description]
+- Step 2.1
+- Step 2.2
+...
+
+### Dependencies
+[List external dependencies, APIs, services needed]
+
+### Risks
+- HIGH: [Critical risks that could block implementation]
+- MEDIUM: [Moderate risks to address]
+- LOW: [Minor concerns]
+
+### Estimated Complexity
+[HIGH/MEDIUM/LOW with time estimates]
+
+**WAITING FOR CONFIRMATION**: Proceed with this plan? (yes/no/modify)
+
+---
+
+**CRITICAL**: Do NOT write any code until the user explicitly confirms with "yes", "proceed", or similar affirmative response.