feat(#10438): add telemetry for visible task count on recalculation

[megha1807]

Description

Fixes #10438
Docs PR:medic/cht-docs#2171

Each time tasks are recalculated in tasks.component.ts, there was no way to know how many tasks are visible to a
user without querying the server directly.

This PR adds a telemetry entry tasks:visible-count that records the number of visible tasks each time refreshTasks()
is called — covering both initial load and subsequent recalculations triggered by changes or rules engine updates.

Changes Made

• Injected TelemetryService into TasksComponent
• Added telemetryService.record('tasks:visible-count', tasksWithLineage.length) after tasks are recalculated
• Added unit test to verify telemetry is recorded with
  the correct key and count

Code review checklist

• Readable: Concise, well named, follows the style guide
• Tested: Unit tests added
• AI disclosure: Used AI assistance for guidance on
  implementation approach and test structure

[dianabarsan]

Great work! One small comment about naming.

[dianabarsan]

I think that using visible is too bespoke here. Please just use tasks:all-tasks, because it matches with other telemetry entries that we have: https://docs.communityhealthtoolkit.org/technical-overview/data/performance/telemetry/

[megha1807]

Hi @dianabarsan, thank you for the feedback!
I have updated the telemetry key from tasks:visible-count to tasks:all-tasks to match the existing naming conventions.

[dianabarsan]

Beautiful!

I will have to ask for a followup PR to cht-docs telemetry to document the new entry.

[megha1807]

Thanks @dianabarsan!

I’ll create a follow-up PR in cht-docs to document the new telemetry entry.

[megha1807]

Hello @dianabarsan
I have made a PR to PR in cht-docs to document the new telemetry entry.
medic/cht-docs#2171