docs: add Directorist settings panel agent guide

[RabbiIslamRony]

PR Type

What kind of change does this PR introduce?

• Bugfix
• Security fix
• Improvement
• New Feature
• Refactoring (no functional changes, no api changes)
• Build related changes
• Text changes
• Other... Please describe:

Summary

Adds a repo-tracked Directorist settings panel agent guide for safe settings-panel redesign and feature planning.

Changes

• Add settings-panel agent docs under docs/agents/directorist-settings-panel/
• Document settings architecture, save behavior, connected systems, limitations, and report-first workflow
• Add settings option catalog covering core, filter-injected, and extension-dependent settings
• Link the settings-panel agent from AGENTS.md and CLAUDE.md
• Exclude /docs from plugin/package exports through .distignore and .gitattributes

Safety

• Documentation-only change
• No runtime plugin behavior changed
• No PHP/Vue/settings save logic changed
• No npm/build commands run

Verification

• Ran git diff --check
• Confirmed docs/ is not gitignored
• Confirmed .distignore excludes /docs
• Confirmed .gitattributes has /docs export-ignore

Any linked issues

Fixes #

Checklist

• My code follows the WordPress coding standards

[RabbiIslamRony]

@Armanul46 Please do not merge this PR until the settings panel design is completed