Sort docs folder filenames by date

[hiiamtrong]

Problem

When multiple phase documents exist in the docs/ai/ subdirectories (e.g. requirements/, design/, planning/), there is no consistent date-based ordering for filenames. This makes it difficult to track the chronological evolution of documents and identify the most recent files at a glance.

Proposed Solution

Add a date prefix convention (e.g. YYYY-MM-DD-) to generated filenames, so files are naturally sorted by date in file explorers and directory listings.

Example:

docs/ai/requirements/
  2026-03-01-initial-requirements.md
  2026-03-10-updated-auth-requirements.md

Alternatively, sort/list files by modification date when reading the docs/ai/ directory tree.

Expected Behavior

• Files within each docs subdirectory should be presented in chronological order
• The most recent document should be easy to identify without checking file metadata

Additional Context

This would improve the AI-assisted development workflow by making it clearer which documents represent the latest state of requirements, design, or planning decisions.