[BUG] Line-by-line text rendering + inconsistent status line since v2.1.76/77

Describe the bug

Two issues that started simultaneously with v2.1.76/v2.1.77:

1. Line-by-line text rendering

Text responses render one line at a time with visible delay between each line, instead of streaming in chunks like previous versions. Code blocks seem unaffected — only prose/text output is slow.

2. Status line inconsistencies

• The "Discombobulating..." spinner/thinking indicator appears intermittently — sometimes it shows, sometimes it doesn't
• The elapsed time counter never shows anymore — previously it would display seconds/minutes while processing

What was tried

• prefersReducedMotion: true — no effect on line-by-line rendering
• Full restart of Claude Code — no effect
• No user config changes were made between working and broken versions

Expected behavior

• Text should stream in chunks as tokens arrive, not line-by-line
• Status line should consistently show the thinking spinner and elapsed time

Environment

Reproduced on two separate machines:

• Machine 1: Windows 11 Home (10.0.22631)
• Machine 2: macOS (Mac Mini)

Both machines updated to v2.1.76 → v2.1.77 and started exhibiting both issues simultaneously. No config changes on either machine.

Additional context

• Related to #34080 (slow text rendering regression) but with a narrower bisect window — this user confirms it started specifically with v2.1.76/77, not earlier
• The simultaneous appearance of both rendering + status line issues suggests a shared root cause in the TUI rendering pipeline