feat(chat): open the settings window from the view header

[luoxuanzao]

Summary

• Add a gear button beside the feedback button in the view header that opens the Qoderian settings page in its own window, so reaching a setting no longer means diving into Obsidian's settings pane and the sidebar/chat stay in place.
• The settings window renders through a new mount(containerEl) entry point that shares the existing imperative builders with the pre-1.13 display() fallback; PluginSettingTab.display() (deprecated since Obsidian 1.13.0) is no longer called anywhere, and the tab keeps its declarative getSettingDefinitions() for 1.13+.
• Adds the settings window styles, a unit test for the modal, and a changelog entry.

Verification

• npm run typecheck
• npm run lint
• npm run test — 165 suites / 3538 tests pass
• Live check in the dev vault (built + window reloaded): the header shows the gear button, clicking it opens the settings window with all 29 setting rows, Esc closes it
• src contains no remaining .display() calls

Safety

• No credentials, private vault content, internal URLs, or personal paths are included
• User-visible changes are documented in CHANGELOG.md

Co-authored-by: QoderAI (Qwen 3.8 Max) qoder_ai@qoder.com