fix(plugin-meetings): reset stale share state during whiteboard handoff

[mickelr]

Summary

Fixes a webinar share-render failure during a whiteboard -> file/content share handoff.

When Locus reports whiteboard.disposition = RELEASED and content.disposition = ACCEPTED, Meeting.setUpLocusMediaSharesListener() used to keep the previous whiteboard_share_active state. That caused the SDK to re-emit whiteboard-start behavior for an already released whiteboard before the real content share was granted.

This PR defaults the computed share status to NO_SHARE, allowing only GRANTED content/whiteboard states to override it. Intermediate/non-active floor states such as ACCEPTED no longer carry stale share state forward.

Root cause

Before this change:

let newShareStatus = this.shareStatus;

If content was ACCEPTED and whiteboard was RELEASED, none of the existing GRANTED/RELEASED/null branches matched, so newShareStatus remained stale as whiteboard_share_active.

Expected behavior after fix

For the failing sequence:

whiteboard_share_active + whiteboard RELEASED + content ACCEPTED -> no_share
no_share + content GRANTED -> remote_share_active

This avoids the spurious MEETING_STARTED_SHARING_WHITEBOARD event and gives consumers a clean whiteboard-stop then remote-share-start handoff.

Tests

Temporarily focused the relevant setUpLocusMediaSharesListener block per plugin-meetings guidance, ran the targeted meeting test file, and removed .only afterward.

cd /Users/mickelr/Workspace/git/webex-js-sdk
source ~/.nvm/nvm.sh
nvm install 22.14
nvm use 22.14
yarn workspace @webex/plugin-meetings test:unit --targets meeting/index.js

Result:

26 passing (116ms)

Also ran:

git --no-pager diff --check -- packages/@webex/plugin-meetings/src/meeting/index.ts packages/@webex/plugin-meetings/test/unit/spec/meeting/index.js

Result: no whitespace/diff-check errors.

[marcin-bazyl]

the fix seems OK, but I don't think it will fix the actual issue with sharing. The issue it's fixing is just an unnecessary notification about whiteboard started when it's already started, so it won't change anything in the app state. It will stop SDK from sending an incorrect CA event about whiteboard, but I don't think that will have any effect on CA either.
However, any fixes in this area are high risk as they will affect whiteboards and screen sharing for all meetings and I don't understand the changes in the unit tests - the existing code in these unit tests seem overly complicated and these changes are hard to read. Are you able to explain all these changes in the tests?