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/tools/check-coverage.ts

@@ -0,0 +1,170 @@
+/**
+ * Check Coverage Tool
+ *
+ * Custom OpenCode tool to analyze test coverage and report on gaps.
+ * Supports common coverage report formats.
+ */
+
+import { tool } from "@opencode-ai/plugin"
+import * as path from "path"
+import * as fs from "fs"
+
+export default tool({
+  description:
+    "Check test coverage against a threshold and identify files with low coverage. Reads coverage reports from common locations.",
+  args: {
+    threshold: tool.schema
+      .number()
+      .optional()
+      .describe("Minimum coverage percentage required (default: 80)"),
+    showUncovered: tool.schema
+      .boolean()
+      .optional()
+      .describe("Show list of uncovered files (default: true)"),
+    format: tool.schema
+      .enum(["summary", "detailed", "json"])
+      .optional()
+      .describe("Output format (default: summary)"),
+  },
+  async execute(args, context) {
+    const threshold = args.threshold ?? 80
+    const showUncovered = args.showUncovered ?? true
+    const format = args.format ?? "summary"
+    const cwd = context.worktree || context.directory
+
+    // Look for coverage reports
+    const coveragePaths = [
+      "coverage/coverage-summary.json",
+      "coverage/lcov-report/index.html",
+      "coverage/coverage-final.json",
+      ".nyc_output/coverage.json",
+    ]
+
+    let coverageData: CoverageSummary | null = null
+    let coverageFile: string | null = null
+
+    for (const coveragePath of coveragePaths) {
+      const fullPath = path.join(cwd, coveragePath)
+      if (fs.existsSync(fullPath) && coveragePath.endsWith(".json")) {
+        try {
+          const content = JSON.parse(fs.readFileSync(fullPath, "utf-8"))
+          coverageData = parseCoverageData(content)
+          coverageFile = coveragePath
+          break
+        } catch {
+          // Continue to next file
+        }
+      }
+    }
+
+    if (!coverageData) {
+      return {
+        success: false,
+        error: "No coverage report found",
+        suggestion:
+          "Run tests with coverage first: npm test -- --coverage",
+        searchedPaths: coveragePaths,
+      }
+    }
+
+    const passed = coverageData.total.percentage >= threshold
+    const uncoveredFiles = coverageData.files.filter(
+      (f) => f.percentage < threshold
+    )
+
+    const result: CoverageResult = {
+      success: passed,
+      threshold,
+      coverageFile,
+      total: coverageData.total,
+      passed,
+    }
+
+    if (format === "detailed" || (showUncovered && uncoveredFiles.length > 0)) {
+      result.uncoveredFiles = uncoveredFiles.slice(0, 20) // Limit to 20 files
+      result.uncoveredCount = uncoveredFiles.length
+    }
+
+    if (format === "json") {
+      result.rawData = coverageData
+    }
+
+    if (!passed) {
+      result.suggestion = `Coverage is ${coverageData.total.percentage.toFixed(1)}% which is below the ${threshold}% threshold. Focus on these files:\n${uncoveredFiles
+        .slice(0, 5)
+        .map((f) => `- ${f.file}: ${f.percentage.toFixed(1)}%`)
+        .join("\n")}`
+    }
+
+    return result
+  },
+})
+
+interface CoverageSummary {
+  total: {
+    lines: number
+    covered: number
+    percentage: number
+  }
+  files: Array<{
+    file: string
+    lines: number
+    covered: number
+    percentage: number
+  }>
+}
+
+interface CoverageResult {
+  success: boolean
+  threshold: number
+  coverageFile: string | null
+  total: CoverageSummary["total"]
+  passed: boolean
+  uncoveredFiles?: CoverageSummary["files"]
+  uncoveredCount?: number
+  rawData?: CoverageSummary
+  suggestion?: string
+}
+
+function parseCoverageData(data: unknown): CoverageSummary {
+  // Handle istanbul/nyc format
+  if (typeof data === "object" && data !== null && "total" in data) {
+    const istanbulData = data as Record<string, unknown>
+    const total = istanbulData.total as Record<string, { total: number; covered: number }>
+
+    const files: CoverageSummary["files"] = []
+
+    for (const [key, value] of Object.entries(istanbulData)) {
+      if (key !== "total" && typeof value === "object" && value !== null) {
+        const fileData = value as Record<string, { total: number; covered: number }>
+        if (fileData.lines) {
+          files.push({
+            file: key,
+            lines: fileData.lines.total,
+            covered: fileData.lines.covered,
+            percentage: fileData.lines.total > 0
+              ? (fileData.lines.covered / fileData.lines.total) * 100
+              : 100,
+          })
+        }
+      }
+    }
+
+    return {
+      total: {
+        lines: total.lines?.total || 0,
+        covered: total.lines?.covered || 0,
+        percentage: total.lines?.total
+          ? (total.lines.covered / total.lines.total) * 100
+          : 0,
+      },
+      files,
+    }
+  }
+
+  // Default empty result
+  return {
+    total: { lines: 0, covered: 0, percentage: 0 },
+    files: [],
+  }
+}