[codex] rename .agent directory to .agents

[andreichenchik]

Problem

The repository still used .agent/ as the agent configuration directory, but we needed to standardize it to .agents/. Keeping mixed naming breaks path-based references and causes workflows/manual commands to read instructions from the old location.

User Impact

Without this rename, automation prompts and contributor guidance can point to stale paths, which leads to failed prompt loads and confusion when running documented commands.

Root Cause

Directory name and references were coupled to .agent/ across docs and workflow prompt text.

Fix

I renamed .agent/ to .agents/ and updated all known references:

• Updated workflow prompt paths in .github/workflows/new-form-request.yml.
• Updated prompt usage examples in .agents/prompts/README.md.
• Updated structure/checklist references in .agents/AGENTS.md.
• Repointed root symlinks AGENTS.md and CLAUDE.md to .agents/AGENTS.md.

Git detected content-preserving renames for the moved files, so history remains traceable.

Validation

• Verified no remaining .agent/ references in the repo via ripgrep.
• Verified symlinks resolve correctly.
• Verified prompt files exist under .agents/prompts/.
• Checked staged diff integrity with git diff --cached --check.