test(display): deflake async PTY tests (widen screen-wait timeout)

[maxlandon]

Problem

The Go workflow failed on the master push for #107 (the v1.2.2 merge):

completion_test.go:28: timed out waiting for "alpha" on screen
--- FAIL: TestAsyncRefreshCompletions (3.02s)

This is unrelated to the merged change (the skip-csi-sequence command). It's a flaky timeout in the PTY-based async-refresh test: under go test -race on a loaded GitHub runner, the PTY/render pipeline is starved (race instrumentation adds several-fold overhead), and the shared 3s screenWaitTimeout was too tight for tests that wait on a background goroutine growing the completion menu. The same code passed on the PR run; locally the test settles in well under 2s.

Fix

Raise screenWaitTimeout (the shared PTY screen-poll ceiling) from 3s to 15s. The pollers return the instant the awaited content appears, so a larger ceiling never slows a passing test — it only caps how long we wait before declaring failure. No production code is touched.

Verification

• TestAsyncRefreshCompletions now completes in ~0.4s under -race.
• Ran the full internal/display suite under -race 5× — all green (~9s each).
• go vet and golangci-lint clean.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 38.33%. Comparing base (aa06d08) to head (56348e2).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #108   +/-   ##
=======================================
  Coverage   38.33%   38.33%           
=======================================
  Files          59       59           
  Lines        9516     9516           
=======================================
  Hits         3648     3648           
  Misses       5785     5785           
  Partials       83       83           

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