ENG-514: Auto-save plugin settings

[trangdoan982]

Summary

• Settings now save automatically, matching Obsidian's native settings behavior
• Removed "Save Changes" button and "unsaved changes" indicator from all 5 settings tabs (General, Node Types, Relation Types, Discourse Relations, Admin Panel)
• Discrete inputs (toggles, dropdowns, color pickers) save immediately on change
• Text inputs with validation (node type name/format, relation type label/complement) save on blur to avoid persisting intermediate typing states
• Validation errors shown inline on the affected row (red text) instead of Notice toasts
• Fixed shared object reference mutation bug where invalid changes could leak into plugin.settings even when validation rejected them

Test plan

https://www.loom.com/share/13522a032c6445af8ccceaff31cde515

• General tab: toggle "Show IDs in frontmatter", change folder paths and hotkey — verify settings persist after closing/reopening settings
• Node Types tab: edit a node type's name, format, description, tag, color, template, folder path — verify each saves correctly
• Node Types tab: set a format to match an existing node type's format — verify inline error appears and the invalid value is NOT saved
• Relation Types tab: edit label, complement, and color — verify saves correctly
• Relation Types tab: set a label or complement to match another relation type — verify inline error on both rows, not saved
• Discourse Relations tab: change source/type/destination dropdowns — verify saves correctly
• Discourse Relations tab: create a duplicate relation — verify inline error on duplicate rows, not saved
• Admin Panel tab: toggle sync mode — verify saves and initializes sync
• Verify no "Save Changes" buttons remain in any tab

🤖 Generated with Claude Code

Closes ENG-514

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[linear]

ENG-514 Change behavior of plugin settings to save automatically

[supabase]

This pull request has been ignored for the connected project zytfjzqyijgagqxrzbmz because there are no changes detected in packages/database/supabase directory. You can change this behaviour in Project Integrations Settings ↗︎.

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