Features/token improvements

[gvreddy04]

This pull request updates the devspec agent guides, work item templates, and pattern documentation to clarify and enforce the "Minimum Necessary Implementation Pattern" across planning, implementation, and review stages. It also streamlines several templates for clarity and better artifact boundaries, and adds explicit guidance for diagrams and evidence logging.

The most important changes are:

Minimum Necessary Implementation Pattern Integration:

• Added the "Minimum Necessary Implementation Pattern" to .github/agents/devspec.implement-task.agent.md, .github/agents/devspec.tasks.agent.md, and .github/agents/devspec.review.agent.md, requiring agents to avoid unnecessary code changes, dependencies, and complexity unless mandated by the finalized brief. This pattern is now referenced and enforced at all major devspec workflow stages.
• Updated implementation and review procedures to explicitly apply this pattern before each task attempt and during review, flagging unnecessary complexity and ensuring only required changes are made.

Task Planning and Execution Guidance:

• Enhanced .github/agents/devspec.tasks.agent.md to default to 3-5 executable tasks, merge similar tasks, and require every task to have a concrete target, validation, and done condition. Standalone refactor or abstraction tasks are now disallowed unless required by the finalized brief.
• Clarified that planned tasks should be as concise as possible and avoid unnecessary splitting or speculative work.

Evidence and Logging Improvements:

• Refined implementation evidence/logging requirements to focus on actual repository changes, validation, and relevant risks or follow-ups, omitting narration of rejected options unless they explain a risk or concern.

Template and Artifact Streamlining:

• Simplified the clarify.md, diagrams.md, and finalize.md templates to remove redundant instructions, clarify artifact boundaries, and reference upstream sources instead of duplicating content.
• Updated diagram guidance to direct reusable diagrams to architecture folders and added explicit references to diagram consistency patterns.

Pattern Documentation:

• Added a detailed definition and checklist for the "Minimum Necessary Implementation Pattern" in .github/prompts/PATTERNS.md.

These changes collectively enforce lean implementation, clearer artifact management, and more maintainable planning and review processes.