fix: Re-initiate subscription telemetry on _reset() to prevent data loss

[samanthataylor3]

Closes #4

Describe your changes:

When a user manually changes time conductor bounds, TelemetryCollection._reset() clears all data and re-requests historical data, but did not re-initiate the subscription. Some subscription providers supply "latest available data" (LAD) on initial subscription. Since the subscription was never reset during _reset(), that initial LAD data from the provider was lost.

Fix: Add this._initiateSubscriptionTelemetry() in _reset(), mirroring what load() already does at lines 170–171. The _initiateSubscriptionTelemetry() method already safely unsubscribes before re-subscribing, so this is safe.

 _reset() {
   this.boundedTelemetry = [];
   this.futureBuffer = [];
   this.emit('clear');
   this._requestHistoricalTelemetry();
+  this._initiateSubscriptionTelemetry();
 }

All call sites that trigger _reset() benefit from this fix:

• _bounds() — on mode change
• _handleUserBoundsChange() — on user-initiated bounds change
• _setTimeSystemAndFetchData() — on time system change

Also removed the stale @todo handle subscriptions more granularly comment since this is now handled.

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Author Checklist

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Reviewer Checklist

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Link to Devin session: https://app.devin.ai/sessions/b42c44263e2f4e49b934c88a2c5e4adb
Requested by: @samanthataylor3

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[devin-ai-integration]

Original prompt from Samantha

Fix GitHub Issue #4 in COG-GTM/openmct: Telemetry Collections dropping data on user bounds change.

#``# Problem
When a user manually changes time conductor bounds, TelemetryCollection._reset() clears all data and re-requests historical data, but does NOT re-initiate the subscription. Some subscription providers supply 'latest available data' on initial subscription. Since the subscription is never reset during _reset(), that initial LAD data from the provider is lost.

#``# Plan

1. Open src/api/telemetry/TelemetryCollection.js
2. In the _reset() method (around line 570), add a call to this._initiateSubscriptionTelemetry() right after this._requestHistoricalTelemetry(). This mirrors what load() already does at lines 170-171.
3. Remove the ``@todo handle subscriptions more granularly comment from the `_reset()` JSDoc since we are now handling it.
4. The _initiateSubscriptionTelemetry() method (line 256) already safely unsubscribes before re-subscribing, so this is safe.
5. Verify existing tests pass (check for TelemetryCollectionSpec.js or similar test files).
6. Add a test that verifies _initiateSubscriptionTelemetry is called when _reset is invoked (e.g., on bounds change).
7. Run npm run lint to ensure no lint errors.
8. Create a PR referencing Issue #4 with a clear description.

#``# Call Sites That Trigger _reset()

• _bounds() line 404 — on mode change
• _handleUserBoundsChange() line 496 — on user-initiated bounds change
• _setTimeSystemAndFetchData() line 555 — on time system change

All three benefit from re-initiating the subscription.

#``# The fix (pseudocode):

_reset() {
    this.boundedTelemetry = [];
    this.futureBuffer = [];
    this.emit('clear');
    this._requestHistoricalTelemetry();
    this._initiateSubscriptionTelemetry(); // <-- ADD THIS LINE
}

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