Add Copilot agent prompt improvement workflow and docs

Added a GitHub Actions workflow for scheduled prompt improvements using the Copilot coding agent, a tailored issue template, and a comprehensive chatmode for prompt engineering in VS Code. Updated README with clear instructions for using the new chatmode and delegating improvements to the Copilot agent. Added TODO.md with setup, usage, and validation steps. Created user prompt for configuring the chatmode and ensured all new files are organized for maintainability and CI/CD best practices.

Author: praeducer

.github/ISSUE_TEMPLATE/prompt-improvement-copilot-agent.yml

@@ -0,0 +1,94 @@
+name: "Prompt Improvement: Copilot Agent"
+description: "Assign the Copilot coding agent to improve prompts with incremental, validated changes."
+title: "[Prompt Improvement] <short title>"
+labels: ["copilot-agent", "prompt-improvement"]
+assignees: ["github-copilot-agent"]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Use this template to delegate iterative prompt improvements to GitHub Copilot coding agent.
+        The agent will create a new branch, open a PR, and iterate based on your PR review comments.
+  - type: input
+    id: scope
+    attributes:
+      label: Target files / scope
+      description: "Paths or globs of prompts to improve (e.g., user_prompts/**, prompt_engineering_assistant.system.prompt.md)."
+      placeholder: "user_prompts/**"
+    validations:
+      required: true
+  - type: dropdown
+    id: improvement_type
+    attributes:
+      label: IMPROVEMENT_TYPE
+      description: "Defines the scope of improvements."
+      options:
+        - incremental
+        - comprehensive
+        - targeted
+      default: 0
+    validations:
+      required: true
+  - type: input
+    id: change_threshold
+    attributes:
+      label: CHANGE_THRESHOLD
+      description: "Percentage threshold for total changes (default 15%)."
+      placeholder: "15%"
+    validations:
+      required: false
+  - type: dropdown
+    id: optimization_focus
+    attributes:
+      label: OPTIMIZATION_FOCUS
+      description: "Primary optimization goal"
+      options:
+        - all
+        - clarity
+        - redundancy
+        - modularity
+      default: 0
+    validations:
+      required: true
+  - type: textarea
+    id: goals
+    attributes:
+      label: Goals and Success Criteria
+      description: "Define the specific goals and measurable success criteria."
+      placeholder: |
+        Goals:
+        - Reduce redundancy without altering behavior
+        - Improve clarity and remove ambiguity
+        Success Criteria:
+        - Maintain all capabilities and guardrails
+        - ≤ 15% diff total change
+    validations:
+      required: true
+  - type: textarea
+    id: instructions
+    attributes:
+      label: Instructions for Copilot
+      description: |
+        High-level guidance for the agent. It will use the repository's prompt system and the custom chat mode content in .github/chatmodes/prompt_engineering_assistant.chatmode.md.
+      placeholder: |
+        - Follow the Prompt Engineering Assistant methodology: Research → Test → Improve → Confirm.
+        - Preserve all existing functionality and guardrails.
+        - Provide clear diffs and concise commit messages.
+        - Add/update minimal tests/docs when public behavior changes.
+        - Keep changes under the CHANGE_THRESHOLD; prefer incremental PRs.
+    validations:
+      required: true
+  - type: textarea
+    id: notes
+    attributes:
+      label: Notes / Context (optional)
+      description: "Links, examples, or constraints."
+      placeholder: |
+        - Reference prompts: user_prompts/*
+        - Keep tone and structure aligned to system prompt.
+  - type: markdown
+    attributes:
+      value: |
+        When ready, submit this issue and assign it to Copilot (Assignee: github-copilot-agent). You can also paste the hashtag below in a VS Code chat to hand off:
+        
+        #github-pull-request_copilot-coding-agent