Auto-generated session titles no longer include the PR number when prompting to review a PR

Start by reproducing the issue in the macOS desktop app with prompts such as "Review PR 1234," comparing title generation in v1.1.21 with v1.1.20 if available. Trace the session-title generation entry point and its handling of pull-request numbers. Done means prompts naming a PR produce distinct titles that include its number, with a regression test covering the behavior.

Short summary

Session titles for PR review prompts dropped the PR number starting in v1.1.21.

Affected version or release

v1.1.21 (macOS). Worked in v1.1.20 or earlier. Not yet tested on v1.1.23.

Installation context

macOS desktop app, project sessions on GitHub repositories.

What happened?

When I start a session by prompting it to review a specific PR, the generated title is now generic and has no PR number. Every PR review session I started after updating to v1.1.21 got the same title. That makes them impossible to tell apart in the sidebar without renaming each one by hand.

Before the update, the same kind of prompt reliably produced titles like "PR 792 review" or "Review PR 799".

Steps to reproduce

1. Start a new session in a project.
2. Prompt it to review a PR by number, for example "Review PR 1234".
3. Wait for the session title to be generated.
4. Observe that the title is generic, with no PR number.

Expected behavior

The generated title includes the PR number when the prompt names one, as it did before v1.1.21.

Additional context

• The changelog doesn't list any change to title generation between v1.1.20 and v1.1.21.
• The v1.1.18 entry "pull request numbers no longer appear inline in sidebar rows" seems unrelated. It covers the badge on sessions linked to a PR, and these sessions aren't linked to one. The number used to be part of the generated title itself.