tui: premium loading + error polish; restore multi-line pull layer log

[deveshctl]

Premium polish pass for the TUI loading and error screens, plus restoration of the multi-line pull progress log.

What changed

Loading screen layout — centered content
Both the loading and error panels were wrapped in a centered border, but the content inside (title, stepper, pull detail, hints) used a hard-coded two-space indent and rendered flush-left. The fix introduces a display-width-aware centerLine helper, drops the manual indentation, and lets each panel grow to fit its own content rather than reserving a fixed minimum height. Result: every row sits on the panel midline.

Multi-line pull progress log
Earlier polish work collapsed the pull progress to a single overwritten line. This restores the running history: as LayersDone advances, the model appends one snapshot per newly-completed layer, rendered dim with a full bar above the in-flight layer (accent, live progress). Capped at five visible rows so a 100-layer pull cannot push the panel off-screen. Falls back gracefully when the daemon reports no byte totals.

Layer 1/12 [━━━━━━━━] 0.4 / 4.7 GB
Layer 2/12 [━━━━━━━━] 0.9 / 4.7 GB
Layer 3/12 [━━━━━━━━] 1.2 / 4.7 GB
Layer 4/12 [━━━━━━  ] 1.4 / 4.7 GB

Error panel — same centering treatment
✕ Error title, error body, recovery hint, and exit hint all align to the panel midline. Recovery hints for ErrDaemonNotRunning and ErrNoEngineFound are preserved verbatim.

What stays the same

Every premium-polish behaviour shipped on this branch is preserved end-to-end: the stepper rail, the elapsed M:SS timer, per-phase glyphs (↓ ▣ ≡ ✓), the cache-hit hold (~300 ms with ready in 0.Xs), the file-viewer loading/binary/empty states, the ?-pinned status bar with success/error colour coding, the CLI recovery hints, the narrow-terminal protections (panel never exceeds terminal width, bytes-total never mid-truncated, progress bar dropped below 4 cells), and the consistent exit vocabulary (Press q or Esc to exit. on full-screen states, Press Esc to close on overlays).

Tests added

• TestViewLoadingLayerLogShowsMultipleLines — multiple Layer N/ rows plus the in-flight row appear together.
• TestViewLoadingContentCentered — at width 80, the ◆ layerx title has meaningful leading padding.
• TestPullLayerLogAppendsOnLayersDoneIncrease — drives progressMsg updates and verifies snapshots accumulate (including a 1→3 jump appending two entries in order).
• TestViewErrorContentCentered — the ✕ Error title is not flush-left.

All existing loading, error, status-bar, file-viewer, and progress-bar tests still pass.

Verification

Verified against a real Docker daemon (multi-layer pull, cache hit, cache bypass with --no-cache), against an OCI / docker-save archive, and under daemon-down conditions to exercise the error path. Cross-compile matrix and unit tests are green on CI for linux/darwin/windows × amd64/arm64.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 79.56656% with 66 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
tui/model.go	79.35%	43 Missing and 15 partials ⚠️
tui/fileview.go	77.77%	4 Missing and 4 partials ⚠️

📢 Thoughts on this report? Let us know!

[deveshctl]

Closing for now — the error-polish work here overlaps with the just-merged #77 and the branch conflicts with main. Will remake against current main later.