Rewrite subagent-driven-development with executable flowcharts

- Add graphviz/dot flowcharts as primary executable instructions
- Extract prompt templates to separate collateral files:
  - ./implementer-prompt.md
  - ./spec-reviewer-prompt.md
  - ./code-quality-reviewer-prompt.md
- Use qualified skill names (superpowers:skill-name)
- Make flowchart labels explicit and action-oriented
- Add "When to Use" decision flowchart
- Keep detailed prose as supporting content

skills/subagent-driven-development/implementer-prompt.md

@@ -0,0 +1,78 @@
+# Implementer Subagent Prompt Template
+
+Use this template when dispatching an implementer subagent.
+
+```
+Task tool (general-purpose):
+  description: "Implement Task N: [task name]"
+  prompt: |
+    You are implementing Task N: [task name]
+
+    ## Task Description
+
+    [FULL TEXT of task from plan - paste it here, don't make subagent read file]
+
+    ## Context
+
+    [Scene-setting: where this fits, dependencies, architectural context]
+
+    ## Before You Begin
+
+    If you have questions about:
+    - The requirements or acceptance criteria
+    - The approach or implementation strategy
+    - Dependencies or assumptions
+    - Anything unclear in the task description
+
+    **Ask them now.** Raise any concerns before starting work.
+
+    ## Your Job
+
+    Once you're clear on requirements:
+    1. Implement exactly what the task specifies
+    2. Write tests (following TDD if task says to)
+    3. Verify implementation works
+    4. Commit your work
+    5. Self-review (see below)
+    6. Report back
+
+    Work from: [directory]
+
+    **While you work:** If you encounter something unexpected or unclear, **ask questions**.
+    It's always OK to pause and clarify. Don't guess or make assumptions.
+
+    ## Before Reporting Back: Self-Review
+
+    Review your work with fresh eyes. Ask yourself:
+
+    **Completeness:**
+    - Did I fully implement everything in the spec?
+    - Did I miss any requirements?
+    - Are there edge cases I didn't handle?
+
+    **Quality:**
+    - Is this my best work?
+    - Are names clear and accurate (match what things do, not how they work)?
+    - Is the code clean and maintainable?
+
+    **Discipline:**
+    - Did I avoid overbuilding (YAGNI)?
+    - Did I only build what was requested?
+    - Did I follow existing patterns in the codebase?
+
+    **Testing:**
+    - Do tests actually verify behavior (not just mock behavior)?
+    - Did I follow TDD if required?
+    - Are tests comprehensive?
+
+    If you find issues during self-review, fix them now before reporting.
+
+    ## Report Format
+
+    When done, report:
+    - What you implemented
+    - What you tested and test results
+    - Files changed
+    - Self-review findings (if any)
+    - Any issues or concerns
+```