Move comprehensive test subtasks into a dedicated task directory

[Copilot]

This reorganizes the comprehensive automated test framework plan so the subtasks are easier to consume, track, and copy into follow-up work. The single root document is replaced with a parent task index plus one concrete markdown file per subtask.

• Task layout

  • move the root-level task document into tasks/comprehensive-test-framework/
  • add tasks/README.md as an entry point for task documents
  • add a parent README.md for the comprehensive test framework task

• Subtask split

  • break the monolithic subtask section into 13 standalone markdown files
  • keep each file scoped to one work item with its own objective, implementation steps, and deliverables
  • preserve the rollout order and parent-level exit criteria in the directory README

• Usability

  • make each subtask directly linkable and easier to assign or paste into an issue tracker
  • keep shared conventions centralized in the parent task README instead of repeating them in every task

tasks/
├── README.md
└── comprehensive-test-framework/
    ├── README.md
    ├── 01-define-validation-scope-and-invariants.md
    ├── 02-build-deterministic-cluster-simulation-harness.md
    ├── ...
    └── 13-add-flake-management-and-quarantine-policy.md

Checklist

• Updated guide with pertinent info (may not always apply).
• Squash down commits to one or two logical commits which clearly describe the work you've done.
• Unittest is a friend:)

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This change is