feat(tui): animated neural pulse spinner with random verbs

[broomva]

Ports the shell's animated glyph system to the TUI. Shows neural pulse animation (·◦○◎●◉●◎○◦) with a random verb instead of static 'Thinking...' text. New verb picked on each RunStarted. 220 tests passing.

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Summary by CodeRabbit

• New Features
  • The app now displays an animated thinking indicator with a continuously updating spinner while processing tasks, replacing the previous static text. This enhancement provides more engaging visual feedback, making it clearer that the application is actively working on requests and progressing through task execution.

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

This PR introduces an animated spinner indicator system for the TUI application. It adds the fastrand dependency, creates a SpinnerKind enum supporting Neural and Tool visualization modes, implements randomized verb selection in the Spinner widget, and integrates the animated spinner throughout the app's state management and UI rendering. Test assertions are updated to verify the new Unicode ellipsis character display.

Changes

Cohort / File(s)	Summary
Dependency Addition crates/arcan-tui/Cargo.toml	Added fastrand = "2" dependency under the Platform section to support randomization.
Spinner Widget Enhancement crates/arcan-tui/src/widgets/spinner.rs	Replaced single fixed frame array with SpinnerKind enum (Neural, Tool) selecting between NEURAL_PULSE and TOOL_FRAMES. Added verb field for dynamic verb text, implemented verb(), new_verb() (randomized via fastrand), set_tool_mode(), and set_neural_mode() APIs. Updated tick() and current() to use frame sets based on active kind.
State Management Integration crates/arcan-tui/src/models/state.rs	Added public spinner: Spinner field to AppState. Initialized spinner on construction and advanced it via new_verb() during AgentEvent::RunStarted.
UI Display Updates crates/arcan-tui/src/widgets/chat_log.rs, crates/arcan-tui/src/app.rs	Replaced static "Thinking…" text with animated spinner: chat_log now renders {glyph} {verb}… using state.spinner.current() and state.spinner.verb(). App now calls self.state.spinner.tick() on TuiEvent::Tick when busy.
Test Assertions crates/arcan-tui/src/e2e_test.rs, crates/arcan-tui/src/integration_test.rs	Updated busy-indicator assertions to expect Unicode ellipsis character (\u{2026}) instead of literal "Thinking" string. Added clarifying comment that animated spinner disappears after RunFinished.

Sequence Diagram

sequenceDiagram
    participant User
    participant App
    participant Spinner
    participant State
    participant ChatLog

    User->>App: Send message to agent
    App->>State: RunStarted event
    State->>Spinner: new_verb() - randomize verb
    State->>State: set is_busy = true

    loop Every Tick Until RunFinished
        App->>Spinner: tick()
        Spinner->>Spinner: advance frame index
        ChatLog->>Spinner: current() - get glyph
        ChatLog->>Spinner: verb() - get verb
        ChatLog->>ChatLog: render {glyph} {verb}…
    end

    User->>App: Agent finishes
    App->>State: RunFinished event
    State->>State: set is_busy = false
    ChatLog->>ChatLog: render without spinner

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~35 minutes

Poem

🐰 With spinners twirling, verbs at play,
The UI dances night and day,
Fastrand picks the words with care,
Neural pulses float through air,
Tools and thoughts now spin so fair! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately reflects the primary change: introducing an animated neural pulse spinner with random verbs in the TUI, replacing static 'Thinking...' text.
Docstring Coverage	✅ Passed	Docstring coverage is 95.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/tui-animated-spinner

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