Commands fixes and updates

[spaghetti-coder]

Fixes #5330

Additional changes:

1. Added a few commands. Criteria for adding a command:
   1. Present in other similar editors, basically same as 1.2
   2. Often needed (one can argue that details is not one of them, but IMO point 1.3 is the exact reason)
   3. Hard to recall / too long to type
2. Fixed an issue from this comment

 
Demo:

demo-shortkeys-1.mp4

[Copilot]

Pull request overview

This PR fixes command functionality in the memo editor by updating the cursor positioning system and adding new commands. It addresses issue #5330 and fixes a click interaction bug in the suggestions popup. The main changes include:

• Migrating from cursorOffset to cursorRange to support text selection after command insertion
• Adding three new commands: details, image, and youtube
• Fixing a focus-loss issue when clicking suggestion items by adding preventDefault()
• Updating existing commands to use the new cursor positioning system with text selection

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
web/src/components/MemoEditor/Editor/commands.ts	Replaces cursorOffset with cursorRange array format, adds details, image, and youtube commands, updates existing commands to select relevant placeholders
web/src/components/MemoEditor/Editor/CommandSuggestions.tsx	Implements cursor positioning logic to handle the new cursorRange format with text selection support
web/src/components/MemoEditor/Editor/SuggestionsPopup.tsx	Adds preventDefault() to mouse down handler to prevent focus loss when selecting suggestions

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