feat(skill): ck — context-keeper v2, persistent per-project memory

Adds the ck (Context Keeper) skill — deterministic Node.js scripts
that give Claude Code persistent, per-project memory across sessions.

Architecture:
- commands/ — 8 Node.js scripts handle all command logic (init, save,
  resume, info, list, forget, migrate, shared). Claude calls scripts
  and displays output — no LLM interpretation of command logic.
- hooks/session-start.mjs — injects ~100 token compact summary on
  session start (not kilobytes). Detects unsaved sessions, git
  activity since last save, goal mismatch vs CLAUDE.md.
- context.json as source of truth — CONTEXT.md is generated from it.
  Full session history, session IDs, git activity per save.

Commands: /ck:init /ck:save /ck:resume /ck:info /ck:list /ck:forget /ck:migrate
Source: https://github.com/sreedhargs89/context-keeper
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

skills/ck/hooks/session-start.mjs

@@ -0,0 +1,217 @@
+#!/usr/bin/env node
+/**
+ * ck — Context Keeper v2
+ * session-start.mjs — inject compact project context on session start.
+ *
+ * Injects ~100 tokens (not ~2,500 like v1).
+ * SKILL.md is injected separately (still small at ~50 lines).
+ *
+ * Features:
+ * - Compact 5-line summary for registered projects
+ * - Unsaved session detection → "Last session wasn't saved. Run /ck:save."
+ * - Git activity since last session
+ * - Goal mismatch detection vs CLAUDE.md
+ * - Mini portfolio for unregistered directories
+ */
+
+import { readFileSync, writeFileSync, existsSync } from 'fs';
+import { resolve } from 'path';
+import { homedir } from 'os';
+import { execSync } from 'child_process';
+
+const CK_HOME         = resolve(homedir(), '.claude', 'ck');
+const PROJECTS_FILE   = resolve(CK_HOME, 'projects.json');
+const CURRENT_SESSION = resolve(CK_HOME, 'current-session.json');
+const SKILL_FILE      = resolve(homedir(), '.claude', 'skills', 'ck', 'SKILL.md');
+
+// ─── Helpers ──────────────────────────────────────────────────────────────────
+
+function readJson(p) {
+  try { return JSON.parse(readFileSync(p, 'utf8')); } catch { return null; }
+}
+
+function daysAgo(dateStr) {
+  if (!dateStr) return 'unknown';
+  const diff = Math.floor((Date.now() - new Date(dateStr)) / 86_400_000);
+  if (diff === 0) return 'today';
+  if (diff === 1) return '1 day ago';
+  return `${diff} days ago`;
+}
+
+function stalenessIcon(dateStr) {
+  if (!dateStr) return '○';
+  const diff = Math.floor((Date.now() - new Date(dateStr)) / 86_400_000);
+  return diff < 1 ? '●' : diff <= 5 ? '◐' : '○';
+}
+
+function gitLogSince(projectPath, sinceDate) {
+  if (!sinceDate || !existsSync(resolve(projectPath, '.git'))) return null;
+  try {
+    const result = execSync(`git -C "${projectPath}" log --oneline --since="${sinceDate}"`, {
+      timeout: 3000, stdio: 'pipe', encoding: 'utf8',
+    }).trim();
+    const commits = result.split('\n').filter(Boolean).length;
+    return commits > 0 ? `${commits} commit${commits !== 1 ? 's' : ''} since last session` : null;
+  } catch { return null; }
+}
+
+function extractClaudeMdGoal(projectPath) {
+  const p = resolve(projectPath, 'CLAUDE.md');
+  if (!existsSync(p)) return null;
+  try {
+    const md = readFileSync(p, 'utf8');
+    const m = md.match(/## Current Goal\n([\s\S]*?)(?=\n## |$)/);
+    return m ? m[1].trim().split('\n')[0].trim() : null;
+  } catch { return null; }
+}
+
+// ─── Session ID from stdin ────────────────────────────────────────────────────
+
+function readSessionId() {
+  try {
+    const raw = readFileSync(0, 'utf8');
+    return JSON.parse(raw).session_id || null;
+  } catch { return null; }
+}
+
+// ─── Main ─────────────────────────────────────────────────────────────────────
+
+function main() {
+  const cwd = process.env.PWD || process.cwd();
+  const sessionId = readSessionId();
+
+  // Load skill (always inject — now only ~50 lines)
+  const skill = existsSync(SKILL_FILE) ? readFileSync(SKILL_FILE, 'utf8') : '';
+
+  const projects = readJson(PROJECTS_FILE) || {};
+  const entry = projects[cwd];
+
+  // Write current-session.json
+  try {
+    writeFileSync(CURRENT_SESSION, JSON.stringify({
+      sessionId,
+      projectPath: cwd,
+      projectName: entry?.name || null,
+      startedAt: new Date().toISOString(),
+    }, null, 2), 'utf8');
+  } catch { /* non-fatal */ }
+
+  const parts = [];
+  if (skill) parts.push(skill);
+
+  // ── REGISTERED PROJECT ────────────────────────────────────────────────────
+  if (entry?.contextDir) {
+    const contextFile = resolve(CK_HOME, 'contexts', entry.contextDir, 'context.json');
+    const context = readJson(contextFile);
+
+    if (context) {
+      const latest = context.sessions?.[context.sessions.length - 1] || {};
+      const sessionDate = latest.date || context.createdAt;
+      const sessionCount = context.sessions?.length || 0;
+
+      // ── Compact summary block (~100 tokens) ──────────────────────────────
+      const summaryLines = [
+        `ck: ${context.name} | ${daysAgo(sessionDate)} | ${sessionCount} session${sessionCount !== 1 ? 's' : ''}`,
+        `Goal: ${context.goal || '—'}`,
+        latest.leftOff ? `Left off: ${latest.leftOff.split('\n')[0]}` : null,
+        latest.nextSteps?.length ? `Next: ${latest.nextSteps.slice(0, 2).join(' · ')}` : null,
+      ].filter(Boolean);
+
+      // ── Unsaved session detection ─────────────────────────────────────────
+      const prevSession = readJson(CURRENT_SESSION);
+      if (prevSession?.sessionId && prevSession.sessionId !== sessionId) {
+        // Check if previous session ID exists in sessions array
+        const alreadySaved = context.sessions?.some(s => s.id === prevSession.sessionId);
+        if (!alreadySaved) {
+          summaryLines.push(`⚠  Last session wasn't saved — run /ck:save to capture it`);
+        }
+      }
+
+      // ── Git activity ──────────────────────────────────────────────────────
+      const gitLine = gitLogSince(cwd, sessionDate);
+      if (gitLine) summaryLines.push(`Git: ${gitLine}`);
+
+      // ── Goal mismatch detection ───────────────────────────────────────────
+      const claudeMdGoal = extractClaudeMdGoal(cwd);
+      if (claudeMdGoal && context.goal &&
+          claudeMdGoal.toLowerCase().trim() !== context.goal.toLowerCase().trim()) {
+        summaryLines.push(`⚠  Goal mismatch — ck: "${context.goal.slice(0, 40)}" · CLAUDE.md: "${claudeMdGoal.slice(0, 40)}"`);
+        summaryLines.push(`   Run /ck:save with updated goal to sync`);
+      }
+
+      parts.push([
+        `---`,
+        `## ck: ${context.name}`,
+        ``,
+        summaryLines.join('\n'),
+      ].join('\n'));
+
+      // Instruct Claude to display compact briefing at session start
+      parts.push([
+        `---`,
+        `## ck: SESSION START`,
+        ``,
+        `IMPORTANT: Display the following as your FIRST message, verbatim:`,
+        ``,
+        '```',
+        summaryLines.join('\n'),
+        '```',
+        ``,
+        `After the block, add one line: "Ready — what are we working on?"`,
+        `If you see ⚠ warnings above, mention them briefly after the block.`,
+      ].join('\n'));
+
+      return parts;
+    }
+  }
+
+  // ── NOT IN A REGISTERED PROJECT ────────────────────────────────────────────
+  const entries = Object.entries(projects);
+  if (entries.length === 0) return parts;
+
+  // Load and sort by most recent
+  const recent = entries
+    .map(([path, info]) => {
+      const ctx = readJson(resolve(CK_HOME, 'contexts', info.contextDir, 'context.json'));
+      const latest = ctx?.sessions?.[ctx.sessions.length - 1] || {};
+      return { name: info.name, path, lastDate: latest.date || '', summary: latest.summary || '—', ctx };
+    })
+    .sort((a, b) => (b.lastDate > a.lastDate ? 1 : -1))
+    .slice(0, 3);
+
+  const miniRows = recent.map(p => {
+    const icon = stalenessIcon(p.lastDate);
+    const when = daysAgo(p.lastDate);
+    const name = p.name.padEnd(16).slice(0, 16);
+    const whenStr = when.padEnd(12).slice(0, 12);
+    const summary = p.summary.slice(0, 32);
+    return `  ${name}  ${icon}  ${whenStr}  ${summary}`;
+  });
+
+  const miniStatus = [
+    `ck — recent projects:`,
+    `  ${'PROJECT'.padEnd(16)}  S  ${'LAST SEEN'.padEnd(12)}  LAST SESSION`,
+    `  ${'─'.repeat(68)}`,
+    ...miniRows,
+    ``,
+    `Run /ck:list · /ck:resume <name> · /ck:init to register this folder`,
+  ].join('\n');
+
+  parts.push([
+    `---`,
+    `## ck: SESSION START`,
+    ``,
+    `IMPORTANT: Display the following as your FIRST message, verbatim:`,
+    ``,
+    '```',
+    miniStatus,
+    '```',
+  ].join('\n'));
+
+  return parts;
+}
+
+const parts = main();
+if (parts.length > 0) {
+  console.log(JSON.stringify({ additionalContext: parts.join('\n\n---\n\n') }));
+}