fix(frontend): restore click-to-open for side elements

[axelray-dev]

Summary

Since 2.11.0, the element side panel opened automatically whenever a message with display="side" elements arrived. In 2.10.x the panel only opened when the user clicked the element link. Closing the panel did not stick, because the next side-element update forced it open again.

Changes

• In MessagesContainer, stop auto-calling setSideView when side elements change.
• Still clear sideView when no side elements remain so a closed/stale panel does not linger.
• Leave click-to-open via onElementRefClick unchanged.
• Add Vitest coverage: new side elements do not auto-open; clearing elements clears an open side view.

Verification

• Vitest frontend/tests/MessagesContainer.spec.tsx (2 tests)
• ESLint, Prettier, and frontend typecheck on touched files

Fixes #2979

---

Summary by cubic

Restores click-to-open for side elements and removes auto-opening of the side panel. Previously the panel opened whenever side elements arrived; now it opens only on click and stays closed otherwise. Fixes #2979.

• Stop auto-calling setSideView; clear sideView when no side elements remain to prevent stale panels.
• Remove side-element tracking refs for simpler logic in MessagesContainer.
• Keep manual open via onElementRefClick.
• Add vitest tests verifying non-auto-open and proper clearing.

^{Written for commit 645bd8e. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 2 files

_{Re-trigger cubic}

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[dokterbob]

@codex review

[dokterbob]

@codex review

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[dokterbob]

Code looks good to me, but I'm no react buff. Are other maintainers still alive? @hayescode @asvishnyakov @sandangel Anyone of you in a better position to verify quality?

Feedback/approval from other users would also help!

[janis-bauer-rsu]

Just a user report in support of this PR: the auto-opening side panel since 2.11.0 is a real annoyance in our app. It affects the UX on every single message with a side element, which makes it hard to live with long-term.

#2979 covered the same regression and was closed as stale while this PR was already open, so it would be a shame to lose it the same way.

[axelray-dev]

I revalidated this PR and merged the current upstream main branch as commit 645bd8e. The targeted Vitest suite passes 2/2, the frontend type-check passes after building the workspace client, and ESLint plus Prettier pass on the changed files. The earlier e2e failure was from the older base; please re-run CI on the updated head. I left the review thread open for verification.