chore: add long-running AI agent playbook scaffolding

[wesleysimplicio]

    Closes #5

Summary

    - add the long-running AI agent playbook scaffolding files
    - append a universal overlay to the existing agent instruction files
    - keep the repository-specific guidance intact

    ## Validation
    - `taskflow inspect /var/folders/4w/3kxdvh6s4ts7rw5h21rk3xr40000gn/T/codex-playbook-o5dazu3b/repo (ok)`

• taskflow run /var/folders/4w/3kxdvh6s4ts7rw5h21rk3xr40000gn/T/codex-playbook-o5dazu3b/repo (ok)

    ## Notes
    - no version bump was applied because this is repository-internal agent scaffolding
    - no existing instruction file was replaced; the change is additive
  

[Copilot]

Pull request overview

Adds long-running AI agent playbook scaffolding (PRD/Progress/Goal Result) and appends a universal overlay section to existing agent instruction files, aiming to standardize long-running session workflow without replacing repo-specific guidance.

Changes:

• Added PRD.md, PROGRESS.md, and GOAL_RESULT.md scaffolding files for long-running agent sessions.
• Appended a “Universal Long-Running Agent Overlay” block to AGENTS.md, CLAUDE.md, and .github/copilot-instructions.md.
• Kept existing instruction content intact and added the overlay additively via marked start/end comments.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
PROGRESS.md	Adds a persistent progress/checkpoint log template for long-running sessions.
PRD.md	Adds a PRD template intended to be the source-of-truth for long-running tasks (needs repo-aligned paths/commands).
GOAL_RESULT.md	Adds a final execution report template for long-running sessions.
CLAUDE.md	Appends the universal long-running overlay section.
AGENTS.md	Appends the universal long-running overlay section.
.github/copilot-instructions.md	Appends the universal long-running overlay section.