feat: enabling session id button for all agents

[MCBoarder289]

Minor change that allows for copying session ids for all agents. Previously it was gated for claude and codex only. Non-prefixed session ids are gracefully handled already.

This is exactly the kind of tool I was looking for, so thank you for building this! I am using Copilot CLI, and was looking for this session id button since it was mentioned in release notes. Hopefully this is a straightforward enough change, but let me know if you have any additional feedback!

[roborev-ci]

roborev: Combined Review (8fc9e44)

Summary Verdict: All agents agree the code is clean and introduces no issues.

Commit 8fc9e44 successfully simplifies the visibility condition
for the session ID button in frontend/src/App.svelte by checking for the presence of session.id rather than specific agent types. No security vulnerabilities or functional defects were detected.

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Synthesized from 4 reviews (agents: codex, gemini | types: default, security)

[wesm]

This was done already in #58, releasing soon