fix(ui): increase default right sidebar width for better terminal readability

[Valley-15]

Fixes #1489

The terminal pane was difficult to use because the right sidebar default
width was only 20%, causing excessive line wrapping for agent output.

This change increases the default sidebar width to improve terminal
readability while keeping the main editor area usable.

[vercel]

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[greptile-apps]

Greptile Summary

Increases the default right sidebar width from 20% to 25% (and adjusts left sidebar from 20% to 18%, center from 60% to 57%) to improve terminal readability for agent output, which previously suffered from excessive line wrapping.

• Default panel layout changed from [20, 60, 20] to [18, 57, 25] in src/renderer/constants/layout.ts
• All new values remain within the defined min/max constraints (LEFT_SIDEBAR_MIN_SIZE=16, RIGHT_SIDEBAR_MAX_SIZE=50, MAIN_PANEL_MIN_SIZE=30) and sum to 100
• Only affects new users or users without persisted layout preferences — existing users with stored sizes in localStorage are unaffected

Confidence Score: 5/5

• This PR is safe to merge — it's a minimal, well-constrained constant change with no logic or behavioral risk.
• The change modifies a single line containing default layout percentages. New values satisfy all existing min/max constraints, sum to 100, and only affect users without persisted layout preferences. No logic changes, no new code paths, no risk of regression.
• No files require special attention.

Important Files Changed

Filename	Overview
src/renderer/constants/layout.ts	Single-line change adjusting default panel layout percentages from [20, 60, 20] to [18, 57, 25]. All values are within existing min/max constraints and sum to 100.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["App mounts"] --> B["usePanelLayout hook"]
    B --> C{"localStorage has\nstored sizes?"}
    C -->|Yes| D["Use stored sizes\n(no change)"]
    C -->|No| E["Use DEFAULT_PANEL_LAYOUT\n[18, 57, 25]"]
    D --> F["clampLeftSidebarSize\n(min 16, max 30)"]
    E --> F
    F --> G["clampRightSidebarSize\n(min 16, max 50)"]
    G --> H["middle = 100 - left - right"]
    H --> I["Render ResizablePanels\nwith defaultSize"]

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_{Last reviewed commit: 3ae14f4}

[shreyaspapi]

Fixes #1489

The terminal pane was difficult to use because the right sidebar default width was only 20%, causing excessive line wrapping for agent output.

This change increases the default sidebar width to improve terminal readability while keeping the main editor area usable.

1. The PR description does not use the template - bad AI sign
2. no screenshot of how it looks by default.

[Valley-15]