docs: Add blog post and new slash commands for development workflow

- Add blog post: 4 Essential Slash Commands I Use in Every Project
- Add new slash commands: /doc-refactor, /setup-ci-cd, /unit-test-expand
- Update slash-commands README with comprehensive documentation
- Simplify /push-all command structure
- Archive add-blog-post-slash-commands change
- Add blog-post spec and pending openspec changes

openspec/changes/archive/2025-12-26-add-blog-post-slash-commands/specs/blog-post/spec.md

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+## ADDED Requirements
+
+### Requirement: Blog Post Directory Structure
+
+The project SHALL provide a `blog-post/` directory for hosting blog-style content that complements the reference documentation.
+
+#### Scenario: Blog post directory exists
+- **WHEN** a user navigates to the project root
+- **THEN** a `blog-post/` directory is present containing blog content
+
+### Requirement: Slash Commands Usage Blog Post
+
+The blog SHALL document 4 essential slash commands with practical usage guidance covering when, where, and how to use each command in a development workflow.
+
+#### Scenario: Complete command coverage
+- **WHEN** a user reads the blog post
+- **THEN** they find documentation for `/push-all`, `/setup-ci-cd`, `/doc-refactor`, and `/unit-test-expand`
+
+#### Scenario: Command file linking for long content
+- **WHEN** a command file exceeds 30 lines
+- **THEN** the blog SHALL provide a link to the full command file in the claude-howto project
+
+#### Scenario: Inline content for short commands
+- **WHEN** a command file is 30 lines or fewer
+- **THEN** the blog MAY include the command content inline
+
+### Requirement: Development Workflow Context
+
+Each command section SHALL explain when to use the command in the development lifecycle (POC, MVP, milestone phases).
+
+#### Scenario: Workflow phase guidance
+- **WHEN** a user reads a command section
+- **THEN** they understand which development phase the command is most appropriate for
+
+### Requirement: Reference to First Blog
+
+The blog post SHALL reference the introductory slash commands blog: "Discovering Claude Code Slash Commands" for foundational context.
+
+#### Scenario: Blog reference present
+- **WHEN** a user reads the introduction
+- **THEN** they find a link to the original slash commands blog post on Medium