[Request Logs]: Fix focus loss on interaction with Purge Actions

[yogeshbhutkar]

What, and Why?

Adds focus management for the request logs purge confirmation flow. When Purge All Logs is clicked, focus moves to Cancel in the confirmation UI. When either Cancel or Yes, Purge All closes the confirmation UI, focus returns to Purge All Logs.

See #589

How?

Uses simple callback refs to focus conditionally rendered buttons as they mount.

Use of AI Tools

AI assistance: Yes
Tool(s): Codex
Model(s): GPT-5.5
Used for: Initial code skeleton; final implementation was reviewed and edited by me.

Testing Instructions

1. Enable the "AI Request Logging" Experiment from Settings → AI.
2. Navigate to Tools → AI Request Logging.
3. Verify that no focus loss occurs when interacting with the confirmation buttons, including focus restoration after clicking Cancel.

Screencast

Before

before.mov

After

after.mov

Changelog Entry

Fixed - Focus loss issues when interacting with Purge actions in the Request Logs experiments page.
Fixed - Disabled the “Purge All” button when no logs are available to purge.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.18%. Comparing base (246680c) to head (91d96ce).

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #599   +/-   ##
==========================================
  Coverage      73.18%   73.18%           
  Complexity      1731     1731           
==========================================
  Files             85       85           
  Lines           7473     7473           
==========================================
  Hits            5469     5469           
  Misses          2004     2004           

Flag	Coverage Δ
unit	73.18% <ø> (ø)

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[github-actions]

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Co-authored-by: yogeshbhutkar <yogeshbhutkar@git.wordpress.org>

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