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/commands/save.mjs

@@ -0,0 +1,210 @@
+#!/usr/bin/env node
+/**
+ * ck — Context Keeper v2
+ * save.mjs — write session data to context.json, regenerate CONTEXT.md,
+ *             and write a native memory entry.
+ *
+ * Usage (regular save):
+ *   echo '<json>' | node save.mjs
+ *   JSON schema: { summary, leftOff, nextSteps[], decisions[{what,why}], blockers[], goal? }
+ *
+ * Usage (init — first registration):
+ *   echo '<json>' | node save.mjs --init
+ *   JSON schema: { name, path, description, stack[], goal, constraints[], repo? }
+ *
+ * stdout: confirmation message
+ * exit 0: success  exit 1: error
+ */
+
+import { readFileSync, mkdirSync, writeFileSync } from 'fs';
+import { resolve } from 'path';
+import {
+  readProjects, writeProjects, loadContext, saveContext,
+  today, shortId, gitSummary, nativeMemoryDir, encodeProjectPath,
+  CONTEXTS_DIR, CURRENT_SESSION,
+} from './shared.mjs';
+
+const isInit = process.argv.includes('--init');
+const cwd    = process.env.PWD || process.cwd();
+
+// ── Read JSON from stdin ──────────────────────────────────────────────────────
+let input;
+try {
+  const raw = readFileSync(0, 'utf8').trim();
+  if (!raw) throw new Error('empty stdin');
+  input = JSON.parse(raw);
+} catch (e) {
+  console.error(`ck save: invalid JSON on stdin — ${e.message}`);
+  console.log('Expected schema (save):  {"summary":"...","leftOff":"...","nextSteps":["..."],"decisions":[{"what":"...","why":"..."}],"blockers":["..."]}');
+  console.log('Expected schema (--init): {"name":"...","path":"...","description":"...","stack":["..."],"goal":"...","constraints":["..."]}');
+  process.exit(1);
+}
+
+// ─────────────────────────────────────────────────────────────────────────────
+// INIT MODE: first-time project registration
+// ─────────────────────────────────────────────────────────────────────────────
+if (isInit) {
+  const { name, path: projectPath, description, stack, goal, constraints, repo } = input;
+
+  if (!name || !projectPath) {
+    console.log('ck init: name and path are required.');
+    process.exit(1);
+  }
+
+  const projects = readProjects();
+
+  // Derive contextDir (lowercase, spaces→dashes, deduplicate)
+  let contextDir = name.toLowerCase().replace(/\s+/g, '-').replace(/[^a-z0-9-]/g, '');
+  let suffix = 2;
+  const existingDirs = Object.values(projects).map(p => p.contextDir);
+  while (existingDirs.includes(contextDir) && projects[projectPath]?.contextDir !== contextDir) {
+    contextDir = `${contextDir.replace(/-\d+$/, '')}-${suffix++}`;
+  }
+
+  const context = {
+    version: 2,
+    name: contextDir,
+    displayName: name,
+    path: projectPath,
+    description: description || null,
+    stack: Array.isArray(stack) ? stack : (stack ? [stack] : []),
+    goal: goal || null,
+    constraints: Array.isArray(constraints) ? constraints : [],
+    repo: repo || null,
+    createdAt: today(),
+    sessions: [],
+  };
+
+  saveContext(contextDir, context);
+
+  // Update projects.json
+  projects[projectPath] = {
+    name: contextDir,
+    contextDir,
+    lastUpdated: today(),
+  };
+  writeProjects(projects);
+
+  console.log(`✓ Project '${contextDir}' registered.`);
+  console.log(`  Use /ck:save to save session state and /ck:resume to reload it next time.`);
+  process.exit(0);
+}
+
+// ─────────────────────────────────────────────────────────────────────────────
+// SAVE MODE: record a session
+// ─────────────────────────────────────────────────────────────────────────────
+const projects = readProjects();
+const projectEntry = projects[cwd];
+
+if (!projectEntry) {
+  console.log("This project isn't registered yet. Run /ck:init first.");
+  process.exit(1);
+}
+
+const { contextDir } = projectEntry;
+let context = loadContext(contextDir);
+
+if (!context) {
+  console.log(`ck: context.json not found for '${contextDir}'. The install may be corrupted.`);
+  process.exit(1);
+}
+
+// Get session ID from current-session.json
+let sessionId;
+try {
+  const sess = JSON.parse(readFileSync(CURRENT_SESSION, 'utf8'));
+  sessionId = sess.sessionId || shortId();
+} catch {
+  sessionId = shortId();
+}
+
+// Check for duplicate (re-save of same session)
+const existingIdx = context.sessions.findIndex(s => s.id === sessionId);
+
+const { summary, leftOff, nextSteps, decisions, blockers, goal } = input;
+
+// Capture git activity since the last session
+const lastSessionDate = context.sessions?.[context.sessions.length - 1]?.date;
+const gitActivity = gitSummary(cwd, lastSessionDate);
+
+const session = {
+  id: sessionId,
+  date: today(),
+  summary: summary || 'Session saved',
+  leftOff: leftOff || null,
+  nextSteps: Array.isArray(nextSteps) ? nextSteps : (nextSteps ? [nextSteps] : []),
+  decisions: Array.isArray(decisions) ? decisions : [],
+  blockers: Array.isArray(blockers) ? blockers.filter(Boolean) : [],
+  ...(gitActivity ? { gitActivity } : {}),
+};
+
+if (existingIdx >= 0) {
+  // Update existing session (re-save)
+  context.sessions[existingIdx] = session;
+} else {
+  context.sessions.push(session);
+}
+
+// Update goal if provided
+if (goal && goal !== context.goal) {
+  context.goal = goal;
+}
+
+// Save context.json + regenerate CONTEXT.md
+saveContext(contextDir, context);
+
+// Update projects.json timestamp
+projects[cwd].lastUpdated = today();
+writeProjects(projects);
+
+// ── Write to native memory ────────────────────────────────────────────────────
+try {
+  const memDir = nativeMemoryDir(cwd);
+  mkdirSync(memDir, { recursive: true });
+
+  const memFile = resolve(memDir, `ck_${today()}_${sessionId.slice(0, 8)}.md`);
+  const decisionsBlock = session.decisions.length
+    ? session.decisions.map(d => `- **${d.what}**: ${d.why || ''}`).join('\n')
+    : '- None this session';
+  const nextBlock = session.nextSteps.length
+    ? session.nextSteps.map((s, i) => `${i + 1}. ${s}`).join('\n')
+    : '- None recorded';
+  const blockersBlock = session.blockers.length
+    ? session.blockers.map(b => `- ${b}`).join('\n')
+    : '- None';
+
+  const memContent = [
+    `---`,
+    `name: Session ${today()} — ${session.summary}`,
+    `description: Key decisions and outcomes from ck session ${sessionId.slice(0, 8)}`,
+    `type: project`,
+    `source: ck`,
+    `sessionId: ${sessionId}`,
+    `---`,
+    ``,
+    `# Session: ${session.summary}`,
+    ``,
+    `## Decisions`,
+    decisionsBlock,
+    ``,
+    `## Left Off`,
+    session.leftOff || '—',
+    ``,
+    `## Next Steps`,
+    nextBlock,
+    ``,
+    `## Blockers`,
+    blockersBlock,
+    ``,
+    ...(gitActivity ? [`## Git Activity`, gitActivity, ``] : []),
+  ].join('\n');
+
+  writeFileSync(memFile, memContent, 'utf8');
+} catch (e) {
+  // Non-fatal — native memory write failure should not block the save
+  process.stderr.write(`ck: warning — could not write native memory entry: ${e.message}\n`);
+}
+
+console.log(`✓ Saved. Session: ${sessionId.slice(0, 8)}`);
+if (gitActivity) console.log(`  Git: ${gitActivity}`);
+console.log(`  See you next time.`);