feat: center branded banner in empty TUI

[EvanProgramming]

Summary

• replace the top-heavy empty transcript card with a centered OpenKyrozen wordmark
• reuse the existing splash identity for one consistent graphite/cyan visual language
• keep one quiet action line below the banner and switch to a single compact line in constrained terminals
• remove the now-unused welcome-card style

Visual behavior

• the banner appears only while the transcript is empty
• conversation content replaces it immediately after the first message
• verified live at 120x30 and 60x16 with the composer, rail, footer, and emergency quit still visible

Validation

• go test ./...
• go vet ./...
• make check
• make lint
• exact terminal bounds checked at 60x16, 80x24, 120x30, and 140x40
• installed binary SHA-256 matches the verified build

TUI only; no web UI, backend protocol, settings schema, dependency, or runtime behavior changes.

Summary by CodeRabbit

• Style
  • Updated the empty conversation view with a centered branded banner, workspace-ready prompt, and workflow hints on larger terminals.
  • Displays a compact ready prompt on smaller terminals.
  • The empty-state banner disappears once conversation messages are present.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: c889d265-9791-4029-bf6a-8abfc02e8183

📥 Commits

Reviewing files that changed from the base of the PR and between 0c35fa0 and f6d298a.

📒 Files selected for processing (3)

• tui/main.go
• tui/main_test.go
• tui/theme.go

💤 Files with no reviewable changes (1)

• tui/theme.go

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📝 Walkthrough

Walkthrough

The TUI empty-history view now displays a branded prompt that adapts to terminal dimensions. Tests cover its content and placement across terminal sizes, and confirm it disappears when conversation messages are present.

Changes

Empty history display

Layer / File(s)	Summary
Render and verify empty history tui/main.go, tui/main_test.go, tui/theme.go	For narrow terminals or short history areas, the empty history shows a compact ready prompt. Otherwise, it displays a centered banner, workspace-ready label, and workflow hints. Tests check content, height, vertical placement, and line widths across terminal sizes, and confirm the banner is absent after messages are added. The unused welcomeStyle is removed.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~8 minutes

Change: Feature

Merge Risk: ⚪ Minimal · up to f6d29

This presentation-only change has no established material regression at the tested sizes. The only identified bounds edge is confined to an effective one-column pane, so the PR appears mergeable.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: centering the branded banner in the empty TUI state.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches 💡 1

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[EvanProgramming]

Closing per request; the final responsive banner-only change was committed directly to main.