Add 6 software development skills

- code-review: critical code review of uncommitted changes
- code-self-review: self-review after writing code
- code-cleanup: garbage collection for technical debt
- security-review: security review from pentester perspective
- create-merge-request: create GitLab MR from uncommitted changes
- understand-project: learn about a project from docs and structure

code-cleanup/SKILL.md

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+---
+name: code-cleanup
+description: >
+  Garbage collection for codebases. Clean up technical debt and entropy by removing dead code,
+  finding duplication, reducing unnecessary complexity, and cleaning up stale comments.
+  Strictly behavior-preserving.
+allowed-tools: bash
+argument-hint: "[file, directory, or 'all']"
+---
+
+# Garbage Collection — Clean Up Technical Debt
+
+You are performing a focused cleanup pass on the codebase. Your goal is to reduce entropy and technical debt by removing what's not needed and simplifying what's left. This is strictly a behavior-preserving operation — nothing should work differently after your changes.
+
+## Scope
+
+Determine what to review:
+- If the user provided a file or directory as $ARGUMENTS, focus on that
+- If the user passed "all", review the main source directories of the project
+- If nothing was provided, ask the user what to target
+
+## Analysis
+
+Go through the target files carefully and check for the following:
+
+### 1. Dead Code
+
+- **Unused functions, methods, classes, or variables** — defined but never called or referenced
+- **Unused imports** — imported but never used in the file
+- **Dead exports** — exported from a module but never imported anywhere else in the project
+- **Commented-out code** — old code left in comments that serves no purpose
+- **Dead dependencies** — packages in dependency files (package.json, requirements.txt, go.mod, etc.) that are installed but never imported anywhere in the codebase
+
+### 2. Duplication and Pattern Inconsistency
+
+- **Duplicated logic** — similar or identical code blocks that could be consolidated into a single function or utility
+- **Inconsistent patterns** — different ways of doing the same thing across the codebase:
+  - Import styles (default vs named, relative vs absolute paths)
+  - How external services/APIs are called (direct fetch vs wrapper, different HTTP clients)
+  - Error handling approaches (try/catch vs .catch, different error formats)
+  - Logging patterns (different loggers, inconsistent log levels or formats)
+  - Configuration access (env vars read directly vs config module)
+- Identify which pattern is the dominant/preferred one and flag the outliers
+
+### 3. Unnecessary Complexity
+
+- **Over-abstraction** — wrapper classes, factories, or patterns that add indirection without adding value
+- **Premature generalization** — code built to handle cases that don't exist and may never exist
+- **Overly clever code** — complex one-liners or convoluted logic that could be written more simply
+- **Unnecessary intermediate variables, transformations, or layers**
+- **Functions that do too much** — could be simplified by removing responsibilities that don't belong
+
+### 4. Stale Comments and TODOs
+
+- **Outdated comments** — comments that describe behavior the code no longer has
+- **Stale TODOs** — TODO/FIXME/HACK comments referencing old issues, completed work, or things no longer relevant
+- **Redundant comments** — comments that just restate what the code obviously does
+
+## Report
+
+Present your findings organized by confidence:
+
+### Safe to Remove
+Items that are clearly dead or unused. No risk of breakage.
+
+### Simplify
+Code that works but is more complex than it needs to be. Include a brief description of how to simplify it.
+
+### Inconsistent Patterns
+List each inconsistency found, which pattern is dominant, and which files are the outliers.
+
+### Verify Before Removing
+Items that appear unused but might be referenced dynamically, via reflection, or from outside the codebase (e.g., API endpoints, CLI handlers, template references). These need manual verification.
+
+## Important Constraints
+
+- **This is behavior-preserving only.** Do not change how anything works.
+- **Do not refactor for style.** Formatting and naming conventions are not in scope unless they are part of a pattern inconsistency.
+- **Present findings first.** Do not make any changes until the user reviews and approves.
+- **Be specific.** Include file names, line numbers, and code snippets for every finding.