fix(theme/Nav): expand navbar item click areas

[SoonIter]

Summary

Follow up on #3629 by making the spacing between navbar items interactive:

• express navbar item spacing as a 32px / 24px gap variable, then apply half of it as padding on each adjacent item so click targets meet without dead space
• use the same item sizing and spacing model for both left- and right-positioned navbar menus
• remove the outer padding from the first and last items, preserving the menu's outer bounds without negative margins
• use a fixed 24px spacing before the left menu, matching the other top-level navbar spacing and removing an unnecessary responsive branch

Validation:

• Prettier check for NavMenu.scss
• git diff --check
• @rspress/core build and Publint for the navbar padding change
• local before/after fixture available at both responsive sizes

The latest variable rename is calculation-equivalent: 32px / 2 = 16px and 24px / 2 = 12px, so it does not change rendered geometry. Repository CI remains the authoritative automated check.

Related Issue

Follow-up to #3629.

Screenshots

Before	After
Navbar items were separated by non-interactive gap, limiting links to their text width	The gap is split into adjacent item padding, making the full horizontal area interactive while keeping the left menu spacing at a consistent 24px

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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Rsdoctor Bundle Diff Analysis

Found 5 projects in monorepo, 3 projects with changes.

📊 Quick Summary

Project	Total Size	Gzip Size	Change	Gzip Change
website_html	14.5 MB	2.1 MB	0	+19.0 B (0.0%)
website_js	16.9 MB	2.9 MB	+180.0 B (0.0%)	+33.0 B (0.0%)
website_md	1.9 MB	278.9 KB	0	0
auto_nav_sidebar_js	546.6 KB	172.6 KB	+180.0 B (0.0%)	+32.0 B (0.0%)
auto_nav_sidebar_html	447.5 KB	93.6 KB	0	0

📋 Detailed Reports (Click to expand)

📁 website_html

Path: website/doc_build/diff-rsdoctor/website_html/rsdoctor-data.json

📌 Baseline Commit: fcdc78f0fc59395802750ae0b13de1466b41ec17 | PR: #3632

Metric	Current	Baseline	Change
📊 Total Size	14.5 MB	14.5 MB	0
🗜️ Gzip Size	2.1 MB	2.1 MB	+19.0 B (0.0%)
📄 JavaScript	0 B	0 B	0
🎨 CSS	0 B	0 B	0
🌐 HTML	14.5 MB	14.5 MB	0
📁 Other Assets	0 B	0 B	0

📦 Download Diff Report: website_html Bundle Diff

📁 website_js

Path: website/doc_build/diff-rsdoctor/website_js/rsdoctor-data.json

📌 Baseline Commit: fcdc78f0fc59395802750ae0b13de1466b41ec17 | PR: #3632

Metric	Current	Baseline	Change
📊 Total Size	16.9 MB	16.9 MB	+180.0 B (0.0%)
🗜️ Gzip Size	2.9 MB	2.9 MB	+33.0 B (0.0%)
📄 JavaScript	16.6 MB	16.6 MB	0
🎨 CSS	168.5 KB	168.3 KB	+180.0 B (0.1%)
🌐 HTML	0 B	0 B	0
📁 Other Assets	177.4 KB	177.4 KB	0

📦 Download Diff Report: website_js Bundle Diff

📁 auto_nav_sidebar_js

Path: e2e/fixtures/auto-nav-sidebar/doc_build/diff-rsdoctor/auto_nav_sidebar_js/rsdoctor-data.json

📌 Baseline Commit: fcdc78f0fc59395802750ae0b13de1466b41ec17 | PR: #3632

Metric	Current	Baseline	Change
📊 Total Size	546.6 KB	546.5 KB	+180.0 B (0.0%)
🗜️ Gzip Size	172.6 KB	172.6 KB	+32.0 B (0.0%)
📄 JavaScript	475.4 KB	475.4 KB	0
🎨 CSS	64.6 KB	64.5 KB	+180.0 B (0.3%)
🌐 HTML	0 B	0 B	0
📁 Other Assets	6.6 KB	6.6 KB	0

📦 Download Diff Report: auto_nav_sidebar_js Bundle Diff

Generated by Rsdoctor GitHub Action

[SoonIter]

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Deploying rspress-v2 with    Cloudflare Pages

Latest commit:	b0f0bec
Status:	✅  Deploy successful!
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Branch Preview URL:	https://codex-optimize-navbar-click.rspress-v2.pages.dev

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