Add new skills and utilities for enhanced writing and testing

- Introduced graphviz conventions for visualizing process flows in writing skills.
- Added a comprehensive guide on persuasion principles to improve skill design effectiveness.
- Implemented a script to render graphviz diagrams from markdown files to SVG format.
- Created a detailed reference for testing skills with subagents, emphasizing TDD principles.
- Established a task tracker template for live task management.
- Developed a shell script to check the integrity of the antigravity profile and required files.
- Added test scripts to validate the initialization of agent projects.
- Created workflows for brainstorming, executing plans, and writing plans to streamline processes.

templates/.agent/skills/single-flow-task-execution/code-quality-reviewer-prompt.md

@@ -0,0 +1,20 @@
+# Code Quality Reviewer Prompt Template
+
+Use this template when running a code quality review step in single-flow mode.
+
+**Purpose:** Verify implementation is well-built (clean, tested, maintainable)
+
+**Only proceed after spec compliance review passes.**
+
+```
+task_boundary:
+  Use template at requesting-code-review/code-reviewer.md
+
+  WHAT_WAS_IMPLEMENTED: [from implementer's report]
+  PLAN_OR_REQUIREMENTS: Task N from [plan-file]
+  BASE_SHA: [commit before task]
+  HEAD_SHA: [current commit]
+  DESCRIPTION: [task summary]
+```
+
+**Code reviewer returns:** Strengths, Issues (Critical/Important/Minor), Assessment