Fix to use "Regenerate" button label and loading state in Title Generation modal

[Intenzi]

What?

Closes #788

Changes button label inside Title Generation modal to "Regenerate" with "Regenerating.." state on click.

Why?

Fixes the User Experience issue where the modal button is provided for regeneration of title. But the button states Generate instead.

How?

• Set "Regenerate" and "Regenerating..." labels for the button modal.
• Uses isRegenerating variable to decide between the two.

Use of AI Tools

AI assistance: Yes
Tool(s): Antigravity IDE
Model(s): Gemini 3.5 Flash (Low)
Used for: Identifying the relevant code file for the fix. Final implementation was reviewed and edited by me.

Testing Instructions

1. Enable Title Generation Experiment.
2. Make a post with sufficient content for Title generation.
3. Click on Generate button to generate Title.
4. A popup modal shows up which asks if you want to regenerate a new title.
5. The button in the popup modal now shows up as "Regenerate"
6. Clicking the Regenerate button here, now shows "Regenerating..."

Screenshots or screencast

Before	After

Changelog Entry

Fixed - Visual Generate button in modal to display Regenerate instead.

[github-actions]

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Co-authored-by: Intenzi <[email protected]>
Co-authored-by: jeffpaul <[email protected]>
Co-authored-by: dkotter <[email protected]>

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.48%. Comparing base (d400910) to head (d3ab6d6).

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #790   +/-   ##
==========================================
  Coverage      76.48%   76.48%           
  Complexity      1869     1869           
==========================================
  Files             89       89           
  Lines           7990     7990           
==========================================
  Hits            6111     6111           
  Misses          1879     1879           

Flag	Coverage Δ
unit	76.48% <ø> (ø)

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[jeffpaul]

Tests well via Playground

[Intenzi]

Labels displayed now are:
Regenerate where applicable:

Generating... instead of Regenerating...