feat: add Cursor, Codex, and OpenCode harnesses — maximize every AI coding tool

- AGENTS.md: universal cross-tool file read by Claude Code, Cursor, Codex, and OpenCode
- .cursor/: 15 hook events via hooks.json, 16 hook scripts with DRY adapter pattern,
  29 rules (9 common + 20 language-specific) with Cursor YAML frontmatter
- .codex/: reference config.toml, Codex-specific AGENTS.md supplement,
  10 skills ported to .agents/skills/ with openai.yaml metadata
- .opencode/: 3 new tools (format-code, lint-check, git-summary), 3 new hooks
  (shell.env, experimental.session.compacting, permission.ask), expanded instructions,
  version bumped to 1.6.0
- README: fixed Cursor section, added Codex section, added cross-tool parity table
- install.sh: now copies hooks.json + hooks/ for --target cursor

.opencode/tools/git-summary.ts

@@ -0,0 +1,56 @@
+/**
+ * ECC Custom Tool: Git Summary
+ *
+ * Provides a comprehensive git status including branch info, status,
+ * recent log, and diff against base branch.
+ */
+
+import { tool } from "@opencode-ai/plugin"
+import { z } from "zod"
+
+export default tool({
+  name: "git-summary",
+  description: "Get comprehensive git summary: branch, status, recent log, and diff against base branch.",
+  parameters: z.object({
+    depth: z.number().optional().describe("Number of recent commits to show (default: 5)"),
+    includeDiff: z.boolean().optional().describe("Include diff against base branch (default: true)"),
+    baseBranch: z.string().optional().describe("Base branch for comparison (default: main)"),
+  }),
+  execute: async ({ depth = 5, includeDiff = true, baseBranch = "main" }, { $ }) => {
+    const results: Record<string, string> = {}
+
+    try {
+      results.branch = (await $`git branch --show-current`.text()).trim()
+    } catch {
+      results.branch = "unknown"
+    }
+
+    try {
+      results.status = (await $`git status --short`.text()).trim()
+    } catch {
+      results.status = "unable to get status"
+    }
+
+    try {
+      results.log = (await $`git log --oneline -${depth}`.text()).trim()
+    } catch {
+      results.log = "unable to get log"
+    }
+
+    if (includeDiff) {
+      try {
+        results.stagedDiff = (await $`git diff --cached --stat`.text()).trim()
+      } catch {
+        results.stagedDiff = ""
+      }
+
+      try {
+        results.branchDiff = (await $`git diff ${baseBranch}...HEAD --stat`.text()).trim()
+      } catch {
+        results.branchDiff = `unable to diff against ${baseBranch}`
+      }
+    }
+
+    return results
+  },
+})