Implement pin comment action for HD Ticket Comments

[Copilot]

Enables comment owners to pin/unpin their comments. Pinned comments appear at the top of ticket activity, maintaining chronological order within pinned and unpinned groups. Pinned comments stick to the top of the viewport when scrolling.

Backend

• Modified get_comments() query to order by is_pinned DESC, creation ASC
• Uses existing is_pinned field from HD Ticket Comment DocType

Frontend

• Added Pin/Unpin action to comment dropdown menu (owner-only)
• Visual pin indicator (Lucide icon) with accessibility label
• Toggle via frappe.client.set_value with toast feedback
• Passed isPinned through activity pipeline from API to CommentBox
• Added sticky positioning (position: sticky; top: 0) to pinned comments so they remain at the top when scrolling
• Applied subtle shadow to sticky comments for visual clarity when content scrolls underneath

Tests

• test_pinned_comments_appear_first() - verifies pinned comments sort before unpinned
• test_multiple_pinned_comments_order() - verifies chronological ordering within groups

Original prompt

Implement a “pin comment” action for HD Ticket Comments so owners can pin/unpin their comments and pinned comments appear at the top of ticket activity. Details:

• Use the existing is_pinned field in helpdesk/helpdesk/doctype/hd_ticket_comment/hd_ticket_comment.json (field label “Is pinned”).
• Locate the computed property that gathers ticket activities and update it to return pinned comments first (preserve relative ordering within pinned and unpinned groups, preferably most-recent-first as today).
• Add a “Pin” action alongside existing owner actions (edit/delete) in the ticket comment UI. When clicked, set is_pinned=1; allow unpinning (toggle) as appropriate.
• Ensure permission checks: only the comment owner should see the pin/unpin action.
• Update any server/API endpoints if required to persist the is_pinned change.
• Add/adjust tests if the repo has existing tests for ticket activities or comment actions.
• Manual verification: pinned comments appear at the top of ticket activity list and remain sticky across reloads.
  Issue context: Pin comments in Ticket #2871.

This pull request was created from Copilot chat.

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[RitvikSardana]

@copilot

now this is how it looks like

what I want is, if the user scrolls below this comment it should stick to the top

[Copilot]

@copilot

...

Added sticky positioning to pinned comments in commit 4c2348a. Pinned comments now use position: sticky with top: 0 and z-index: 10, so they will stick to the top of the viewport when you scroll down past them.

The implementation applies the sticky behavior to the activity wrapper div when activity.type === 'comment' && activity.isPinned is true, with a white background to prevent content from showing through.