fix: zettel id uses formatted time, and title as suffix if provided

[thorinf]

Fix note_id_func to use title parameter and readable timestamps

What does the PR do?

Changes for zettel id when creating a new note, improving file naming:

• Zettel ID will use a more readable version of time.
• If the title is provided it's formatted and used as a suffix.
• Removed the random 4 letters as suffix.

Before: :Obsidian new "My Note" -> 1758908292-NZNT.md
After: :Obsidian new "My Note" -> 202509261930-my-note.md

Very happy to be corrected if the Unix timestamp and random letters is better, this just feels more intuitive as a default to me.

If the change isn't good then I would like to suggest adding the note_id_func override as a commented section in the install snippets.

PR Checklist

• The PR contains a description of the changes
• I read the [CONTRIBUTING.md] file
• The CHANGELOG.md is updated
• The changes are documented in the README.md file
• The code complies with make chores (for style, lint, types, and tests)

[neo451]

Thank you for the PR. Here's my thoughts:

1. the old and your new zettel approach are both very specific approach that one can do for note_id_func. And yours is undoubtedly better.
2. Obsidian app has another two approaches, one with just title as id, one with an even simpler zettel id, where it is just a timestamp.
3. Since we have already have a option that gives so many possibility, the default one should be the least opinionated one (title as id). This has just been a change on my mind that should be executed on 4.0.0, which is a major breaking change.
4. So I believe your example should be in the wiki, I just opened a new page here, you can add a new section, and link to it in the comment in this PR, thanks. https://github.com/obsidian-nvim/obsidian.nvim/wiki/Recipes