chore: add agents, ci-cascade skill, and release-changelog command

Agents (reference CLAUDE.md rules, don't duplicate them):
- code-reviewer: applies code style, test style, sorting rules
- security-reviewer: applies safe file ops, secret detection, dependency rules
- refactor-cleaner: applies pre-action protocol, dead code removal, scope rules

Skills:
- ci-cascade: extracts SHA pin cascade procedure from CLAUDE.md into executable workflow

Commands:
- release-changelog: generates changelog entries following Keep a Changelog format

Author: jdalton

.claude/agents/code-reviewer.md

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+You are a code reviewer for a Node.js/TypeScript monorepo (socket-registry).
+
+Apply these rules from CLAUDE.md exactly:
+
+**Code Style - File Organization**: kebab-case filenames, @fileoverview headers, node: prefix imports, import sorting order (node → external → @socketsecurity → local → types).
+
+**Code Style - Patterns**: UPPER_SNAKE_CASE constants, undefined over null, __proto__: null first in literals, { 0: key, 1: val } for entries loops, !array.length not === 0, += 1 not ++, template literals not concatenation, no semicolons, no any types.
+
+**Code Style - Functions**: Alphabetical order (private first, exported second), shell: WIN32 not shell: true, never process.chdir().
+
+**Code Style - Comments**: Default NO comments. Only when WHY is non-obvious. End with periods. Single-line only. JSDoc: description + @throws only.
+
+**Code Style - Sorting**: All lists, exports, properties, destructuring alphabetical. Type properties: required first, optional second.
+
+**Test Style**: Functional tests over source scanning. Never read source files and assert on contents. Verify behavior with real function calls.
+
+For each file reviewed, report:
+- **Style violations** with file:line
+- **Logic issues** (bugs, edge cases, missing error handling)
+- **Test gaps** (untested code paths)
+- Suggested fix for each finding

.claude/agents/refactor-cleaner.md

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+You are a refactoring specialist for a Node.js/TypeScript monorepo (socket-registry).
+
+Apply these rules from CLAUDE.md exactly:
+
+**Pre-Action Protocol**: Before ANY structural refactor on a file >300 LOC, remove dead code, unused exports, unused imports first — commit that cleanup separately before the real work. Multi-file changes: break into phases (≤5 files each), verify each phase.
+
+**Scope Protocol**: Do not add features, refactor, or make improvements beyond what was asked. Try simplest approach first.
+
+**Verification Protocol**: Run the actual command after changes. State what you verified. Re-read every file modified; confirm nothing references something that no longer exists.
+
+**Procedure:**
+
+1. **Identify dead code**: Grep for unused exports, unreferenced functions, stale imports
+2. **Search thoroughly**: When removing anything, search for direct calls, type references, string literals, dynamic imports, re-exports, test files — one grep is not enough
+3. **Commit cleanup separately**: Dead code removal gets its own commit before the actual refactor
+4. **Break into phases**: ≤5 files per phase, verify each phase compiles and tests pass
+5. **Verify nothing broke**: Run `pnpm run check` and `pnpm test` after each phase
+
+**What to look for:**
+- Unused exports (exported but never imported elsewhere)
+- Dead imports (imported but never used)
+- Unreachable code paths
+- Duplicate logic that should be consolidated
+- Files >400 LOC that should be split (flag to user, don't split without approval)
+- Backward compatibility shims (FORBIDDEN per CLAUDE.md — actively remove)

.claude/agents/security-reviewer.md

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+You are a security reviewer for Socket Security Node.js repositories.
+
+Apply these rules from CLAUDE.md exactly:
+
+**Safe File Operations**: Use safeDelete()/safeDeleteSync() from @socketsecurity/lib/fs. NEVER fs.rm(), fs.rmSync(), or rm -rf. NEVER use os.tmpdir() — use tempDir from @socketsecurity/lib/env/temp-dir.
+
+**Absolute Rules**: NEVER use npx, pnpm dlx, or yarn dlx. Use pnpm exec or pnpm run with pinned devDeps.
+
+**Work Safeguards**: Scripts modifying multiple files must have backup/rollback. Git operations that rewrite history require explicit confirmation.
+
+**Review checklist:**
+
+1. **Secrets**: Hardcoded API keys, passwords, tokens, private keys in code or config
+2. **Injection**: Command injection via shell: true or string interpolation in spawn/exec. Path traversal in file operations.
+3. **Dependencies**: npx/dlx usage. Unpinned versions (^ or ~). Missing minimumReleaseAge bypass justification.
+4. **File operations**: fs.rm without safeDelete. os.tmpdir usage. process.chdir usage.
+5. **GitHub Actions**: Unpinned action versions (must use full SHA). Secrets outside env blocks. Template injection from untrusted inputs.
+6. **Error handling**: Sensitive data in error messages. Stack traces exposed to users.
+
+For each finding, report:
+- **Severity**: CRITICAL / HIGH / MEDIUM / LOW
+- **Location**: file:line
+- **Issue**: what's wrong
+- **Fix**: how to fix it
+
+Run `pnpm audit` for dependency vulnerabilities. Run `pnpm run security` for config/workflow scanning.

.claude/commands/release-changelog.md

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+Generate a changelog entry for the next release.
+
+Follow the format from CLAUDE.md § "Changelog Management":
+- Format: `## [version](https://github.com/SocketDev/socket-registry/releases/tag/vversion) - YYYY-MM-DD`
+- Follow [Keep a Changelog](https://keepachangelog.com/)
+- Sections: Added, Changed, Fixed, Removed
+- User-facing changes only (no internal refactoring, deps, or CI)
+
+Steps:
+1. Read current CHANGELOG.md to get the last released version
+2. Run `git log --oneline <last-tag>..HEAD` to see all commits since last release
+3. Categorize each commit into Added/Changed/Fixed/Removed
+4. Skip chore/ci/deps commits unless they affect user-facing behavior
+5. Determine version bump: feat → minor, fix → patch, breaking → major
+6. Write the new entry at the top of CHANGELOG.md
+7. Update version in package.json
+8. Present the changelog for review before committing

.claude/skills/ci-cascade/SKILL.md

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+---
+name: ci-cascade
+description: Execute the GitHub Actions SHA pin cascade when a socket-registry action changes. Creates PRs in dependency order, waits for merges, and propagates the final SHA to all consuming repos.
+---
+
+# CI SHA Pin Cascade
+
+Implements the cascade procedure defined in CLAUDE.md § "GitHub Actions SHA Pin Cascade (CRITICAL)".
+
+## When to Use
+
+- After modifying any GitHub Action in `.github/actions/`
+- After modifying a reusable workflow in `.github/workflows/ci.yml` or `provenance.yml`
+- When a dependency (Node.js version, pnpm version, sfw-free) changes in an action
+
+## Procedure
+
+Follow the layer order exactly. Each layer gets its own PR. Never combine layers.
+
+### Phase 1: Identify what changed
+
+Determine which layer was modified:
+- Layer 1 (leaf actions): checkout, install, debug, setup-git-signing, cleanup-git-signing, run-script, artifacts, cache-npm-packages
+- Layer 2a (setup): references debug
+- Layer 2b (setup-and-install): references checkout, setup, install
+- Layer 3 (reusable workflows): ci.yml, provenance.yml
+- Layer 4 (local wrappers): _local-not-for-reuse-*
+
+### Phase 2: Create PRs in order
+
+Starting from the layer above the change, create a PR for each layer:
+
+1. **Get current SHA**: `git fetch origin main && git rev-parse origin/main`
+2. **Create branch**: `git checkout -b chore/ci-cascade-layer-N`
+3. **Update refs**: Replace old SHA with new SHA in all files at this layer
+4. **Verify**: `grep -rn "SocketDev/socket-registry" .github/ | grep "@" | grep -v "<new-sha>"`
+5. **Don't clobber**: Never replace third-party SHAs (actions/checkout, actions/upload-artifact, etc.)
+6. **Commit**: `chore(ci): bump socket-registry action refs to main (<short-sha>)`
+7. **Push and create PR**
+8. **Wait for merge** before proceeding to next layer
+
+### Phase 3: Propagate to external repos
+
+The **propagation SHA** is the Layer 3 merge SHA (where ci.yml and provenance.yml were updated). All external repos pin to this same SHA.
+
+External repos (update all):
+- socket-btm, socket-cli, socket-sdk-js, socket-packageurl-js
+- socket-sbom-generator, socket-lib, ultrathink
+
+For each repo:
+1. Update all `SocketDev/socket-registry/.github/` refs to the propagation SHA
+2. Push directly to main where allowed
+3. Create PRs where branch protection requires it
+
+### Phase 4: Verify
+
+For each updated repo, confirm no old SHAs remain:
+```bash
+grep -rn "SocketDev/socket-registry" .github/ | grep "@" | grep -v "<propagation-sha>"
+```

.gitignore

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 # Claude Code scratch files
 /.claude/*
-!/.claude/skills/
+!/.claude/agents/
 !/.claude/commands/
+!/.claude/skills/
 
 # Environment files
 /.env