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.

CURRENT-FLOW.md

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+# Antigravity Superpowers Current Flow
+
+This document explains the active workflow used by the Antigravity profile in this folder.
+
+## 1) Session Start
+
+1. Load rules from `.agent/AGENTS.md`.
+2. Load `.agent/skills/using-superpowers/SKILL.md`.
+3. Before any action, check whether a relevant skill should be loaded from:
+   - `.agent/skills/<skill-name>/SKILL.md` (preferred)
+   - `~/.gemini/skills/<skill-name>/SKILL.md` (fallback)
+4. Ensure `<project-root>/docs/plans/task.md` exists as a list-only table (no instructions).
+
+## 2) Skill-First Routing
+
+For each user request:
+
+1. Identify the best matching skill.
+2. Announce and follow that skill.
+3. If the skill has a checklist, track progress in `<project-root>/docs/plans/task.md`.
+
+## 3) Design Before Implementation
+
+If the request involves creating/changing behavior:
+
+1. Run `brainstorming`.
+2. Explore context and ask clarifying questions.
+3. Propose approaches and get approval.
+4. Write design doc to `docs/plans/YYYY-MM-DD-<topic>-design.md`.
+5. Move to `writing-plans`.
+
+## 4) Planning Stage
+
+`writing-plans` creates a detailed implementation plan:
+
+1. Save plan to `docs/plans/YYYY-MM-DD-<feature-name>.md`.
+2. Break work into small, verifiable steps.
+3. Include exact files, commands, and expected outputs.
+4. Handoff to execution via `.agent/workflows/execute-plan.md` (single entrypoint).
+5. The workflow loads `executing-plans`, which enforces `single-flow-task-execution` rules.
+
+## 5) Execution Model (Single-Flow)
+
+Core execution rules from `.agent/AGENTS.md` and `single-flow-task-execution`:
+
+1. One active task at a time.
+2. One coding execution thread at a time.
+3. Use `task_boundary` for coding tasks.
+4. Use `browser_subagent` only for browser-specific tasks.
+5. Update `<project-root>/docs/plans/task.md` on every task state change.
+
+Per-task loop:
+
+1. Mark task `in_progress`.
+2. Implement scoped change.
+3. Run verification commands.
+4. Fix and re-run until passing.
+5. Mark task `done` with notes.
+
+## 6) Verification Gate
+
+Before any completion claim (`verification-before-completion`):
+
+1. Identify the command that proves the claim.
+2. Run it now (fresh).
+3. Read full output and exit code.
+4. Report evidence.
+5. Only then claim completion.
+
+## 7) Finish Branch
+
+After all tasks are complete and verified (`finishing-a-development-branch`):
+
+1. Re-run required tests.
+2. Present workflow options (merge, PR, keep branch, discard).
+3. Execute selected option safely.
+4. Require explicit confirmation for destructive actions.
+
+## 8) Profile Validation Flow
+
+Validate this profile itself with:
+
+```bash
+bash templates/.agent/tests/run-tests.sh
+```
+
+`run-tests.sh` calls `check-antigravity-profile.sh`, which verifies:
+
+- Required files exist
+- Skill frontmatter is valid
+- Legacy patterns are removed
+- AGENTS mapping contract is present
+
+## Flow Diagram
+
+```mermaid
+flowchart TD
+sessionStart[Session start] --> useSkill[Load using-superpowers]
+useSkill --> routeSkill[Select and load relevant skill]
+routeSkill --> designGate{Behavior/design change?}
+designGate -->|yes| brainstorming[Brainstorming]
+brainstorming --> writingPlans[Writing plans]
+designGate -->|no| execution[Single-flow execution]
+writingPlans --> execution
+execution --> verify[Verification before completion]
+verify --> finish[Finish development branch]
+finish --> done[Done]
+```