Ensure annotations on empty entries in notebook are not lost

[scottbell]

Closes #6156 #6411

Describe your changes:

Don't (sometimes) delete entries if text is empty. Select and focus entries when created.

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Author Checklist

• Changes address original issue?
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[codecov]

Codecov Report

Merging #6525 (78b993e) into master (bc3a540) will increase coverage by 0.01%.
The diff coverage is 40.00%.

@@            Coverage Diff             @@
##           master    #6525      +/-   ##
==========================================
+ Coverage   54.74%   54.76%   +0.01%     
==========================================
  Files         628      628              
  Lines       26802    26805       +3     
  Branches     2421     2422       +1     
==========================================
+ Hits        14673    14680       +7     
+ Misses      11465    11459       -6     
- Partials      664      666       +2     

Flag	Coverage Δ		*Carryforward flag
e2e-ci	39.34% <ø> (ø)		Carriedforward from ae8250d
e2e-full	51.06% <ø> (ø)		Carriedforward from ae8250d
e2e-stable	55.57% <100.00%> (+0.08%)	⬆️
unit	48.93% <0.00%> (-0.05%)	⬇️

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
src/plugins/notebook/components/Notebook.vue	20.39% <0.00%> (-0.24%)	⬇️
src/plugins/notebook/components/NotebookEntry.vue	17.74% <0.00%> (+0.94%)	⬆️
src/plugins/notebook/utils/notebook-entries.js	81.44% <100.00%> (+1.22%)	⬆️

... and 5 files with indirect coverage changes

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[unlikelyzero]

This looks great, but there are several references in this script to remove

openmct/e2e/tests/functional/plugins/notebook/tags.e2e.spec.js

Lines 134 to 135 in e57eedc

	// TODO can be removed with fix for https://github.com/nasa/openmct/issues/6411
	await page.locator('[aria-label="Notebook Entry"].is-selected div.c-ne__text').click();

[ozyx]

LGTM