fix: fill viewport with ghost loader rows on initial load

[spike-rabbit]

What kind of change does this PR introduce? (check one with "x")

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

When using server-side scrolling with ghostLoadingIndicator, only a single undefined row was pushed into _internalRows, resulting in just one or two ghost skeleton rows visible during initial load instead of filling the entire viewport.

What is the new behavior?

Now pushes enough undefined rows to fill the viewport (pageSize - rows.length, minimum 1), so the ghost loader fills the entire body area before data arrives. When data already fills the viewport, only one undefined row is added as a bottom loading indicator.

Does this PR introduce a breaking change? (check one with "x")

• Yes
• No

Other information:

Affects the Scrolling server-side example

Added unit tests verifying:

• Ghost rows fill viewport when loading with no data
• Only one ghost row added as bottom indicator when data fills viewport
• Ghost rows fill remaining space when partial data is loaded
• No ghost rows added when ghostLoadingIndicator is false
• No ghost rows added when scrollbarV is false

[gemini-code-assist]

Code Review

This pull request updates the ghost loading logic in ngx-datatable to fill the viewport with ghost rows by calculating the difference between the page size and the current row count. It also introduces a suite of unit tests to verify this behavior under various conditions. A critical issue was identified where calling pageSize() within the _internalRows computed signal creates a circular dependency and a potential infinite loop if rowHeight is zero; a suggestion was provided to calculate viewport capacity directly to avoid these issues.

[Copilot]

Pull request overview

Fixes ghost loading behavior for server-side scrolling so the initial skeleton rows fill the viewport instead of only rendering 1–2 rows, improving perceived loading behavior in the Scrolling server-side example.

Changes:

• Introduces a viewportRowCount computed value to represent how many rows fit in the visible body.
• Updates ghost-loading logic to append enough undefined rows to fill the viewport (minimum 1).
• Updates calcPageSize() to reuse the shared viewport row count logic.
• Adds unit tests covering ghost row behavior across empty/partial/full data and feature toggles.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
projects/ngx-datatable/src/lib/components/datatable.component.ts	Computes viewport row count and uses it to generate ghost rows and page size under virtualization.
projects/ngx-datatable/src/lib/components/datatable.component.spec.ts	Adds tests asserting ghost row counts under various loading/data conditions.

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