fix(renderer): use view height before first flush

[fzlzjerry]

Fixes #1740.

Before

Create an 80x24 renderer, render a one-line inline view, and call insertAbove before the first flush. The cell buffer still has the terminal height at that point, so the renderer emits ESC[24B and scrolls the viewport.

After

Before the first inline flush, insertAbove calculates its cursor movement from the current view height. Once a view has been flushed, it continues using the cell buffer height so the cursor math stays tied to what is actually on screen. Alt-screen behavior is unchanged.

The regression test exercises the pre-flush call order directly and verifies the complete output sequence for a one-line view.

Tests

• go test ./...

• go test -race -count 4 -cpu 1,4 ./...

• golangci-lint run

• I have read CONTRIBUTING.md.

• I have created a discussion that was approved by a maintainer (not applicable: this is a bug fix for [v2] tea.Printf/Println before the first flush emits a full-terminal-height cursor-down (scrolls the whole screen) #1740).

[Copilot]

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[andrinoff]

Thank you for your contribution!, please fix the comment below! Nice catch!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.46%. Comparing base (351d215) to head (40bf5ab).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1766      +/-   ##
==========================================
+ Coverage   56.50%   58.46%   +1.96%     
==========================================
  Files          25       25              
  Lines        1315     1317       +2     
==========================================
+ Hits          743      770      +27     
+ Misses        482      453      -29     
- Partials       90       94       +4     

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[andrinoff]

sorry, meant to request changes