enhance(ui): tweak tooltip style and misc fixes (#38524)

Tooltip changes:

- center tooltips over their target (default placement `top` instead of
`top-start`)
- fix the arrow rendering off-center on references narrower than 22px
like 16px icons, caused by tippy's hardcoded 3px arrow padding
- fix arrowed tooltips overlapping their reference by 1px because the
offset distance was derived from the raw arrow option
- tweak tooltip colors and reduce content padding
- fix a Firefox bug where lazily created tooltips would not show on the
first hover, because Firefox skips enter/leave event dispatch when no
such listener existed in the window at the time of the pointer crossing

Other UI tweaks:

- tweak repo sidebar release style
- enhance actions back link
- center step chevron
- add border on workflow graph

<img width="92" height="76" alt="Screenshot 2026-07-21 at 18 07 42"
src="https://github.com/user-attachments/assets/968a51de-e470-48c0-b592-4a207dfcbb63"
/>
<img width="94" height="76" alt="Screenshot 2026-07-21 at 18 07 53"
src="https://github.com/user-attachments/assets/5e8e0ce3-7536-4689-a6ae-9cfb6e867ddb"
/>


<img width="203" height="77" alt="Screenshot 2026-07-19 at 00 14 32"
src="https://github.com/user-attachments/assets/71c16a54-ad14-4636-8af4-e68b3599f1d0"
/>
<img width="309" height="290" alt="Screenshot 2026-07-18 at 23 37 21"
src="https://github.com/user-attachments/assets/29630504-d69a-4e23-978b-41ae6d0bff92"
/>
<img width="151" height="110" alt="Screenshot 2026-07-18 at 23 35 47"
src="https://github.com/user-attachments/assets/b8107602-12f1-4f9b-a3f6-b930af25c9e7"
/>

---------

Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/repo/home_sidebar_bottom.tmpl

@@ -7,15 +7,15 @@
 			</a>
 			<span class="ui small label">{{.NumReleases}}</span>
 		</div>
-		<div class="flex-relaxed-list">
+		<div>
 			<div class="flex-text-block">
 				<div>{{svg "octicon-tag"}}</div>
-				<a class="gt-ellipsis muted" href="{{.LatestRelease.Link}}" title="{{.LatestRelease.Title}}">{{.LatestRelease.Title}}</a>
+				<a class="gt-ellipsis muted" href="{{.LatestRelease.Link}}" title="{{.LatestRelease.Title}}"><strong>{{.LatestRelease.Title}}</strong></a>
 				<div class="tw-shrink-0">
 					{{template "repo/release/label" (dict "Release" .LatestRelease "IsLatest" true)}}
 				</div>
 			</div>
-			<div class="tw-ml-[24px]">{{DateUtils.TimeSince .LatestRelease.CreatedUnix}}</div>
+			<div class="tw-ml-[24px] tw-text-12">{{DateUtils.TimeSince .LatestRelease.CreatedUnix}}</div>
 		</div>
 	{{end}}
 
@@ -28,7 +28,7 @@
 		<div>
 			<div class="language-stats">
 				{{range .LanguageStats}}
-				<div class="bar" style="width: {{.Percentage}}%; background-color: {{.Color}}" data-tooltip-placement="top" data-tooltip-content="{{.Language}}" data-tooltip-follow-cursor="horizontal"></div>
+				<div class="bar" style="width: {{.Percentage}}%; background-color: {{.Color}}" data-tooltip-content="{{.Language}}" data-tooltip-follow-cursor="horizontal"></div>
 				{{end}}
 			</div>
 			<div class="language-stats-details">

templates/repo/home_sidebar_top.tmpl

@@ -63,7 +63,7 @@
 				{{svg "octicon-cross-reference"}} {{ctx.Locale.Tr "repo.cite_this_repo"}}
 			</a>
 		{{end}}
-		<div class="flex-text-block muted" {{if not (eq .Repository.Size 0)}}data-tooltip-placement="top" data-tooltip-content="{{.Repository.SizeDetailsString}}"{{end}}>
+		<div class="flex-text-block muted" {{if not (eq .Repository.Size 0)}}data-tooltip-content="{{.Repository.SizeDetailsString}}"{{end}}>
 			{{$fileSizeFormatted := FileSize .Repository.Size}}{{/* the formatted string is always "{val} {unit}" */}}
 			{{$fileSizeFields := StringUtils.Split $fileSizeFormatted " "}}
 			{{svg "octicon-database"}} <b>{{ctx.Locale.PrettyNumber (index $fileSizeFields 0)}}</b> {{index $fileSizeFields 1}}