fix: duplicate view-transition-name when posts share the same title

[WXY-V1hZ]

Description

When two posts have the same frontmatter title, the listing page (Card.astro) generates duplicate view-transition-name values for the article cards. The browser's View Transition API requires unique transition names within a page — duplicates cause the API to silently abort, falling back to a hard (non-animated) navigation.

This can be confusing for users: the page transition animation simply disappears without any error message, making it feel like a browser issue.

Root cause: toTransitionName(title) is called with the post title, which is not guaranteed to be unique. When two posts share a title (e.g., two articles named "Getting Started"), both <h2> elements on the listing page end up with the same view-transition-name.

Fix: Replace title with the content collection id (the unique file path) when generating transition names. The id is inherently unique since no two articles can share the same file path.

This fix applies to both places where transition names are set:

• src/components/Card.astro (listing page cards)
• src/pages/posts/[...slug]/index.astro (detail page heading)

Both must be updated together — if only one side is changed, the heading won't animate smoothly during navigation.

Types of changes

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Documentation Update (if none of the other choices apply)
• Others (any other types not listed above)

Checklist

• I have read the Contributing Guide
• I have added the necessary documentation (if appropriate)
• Breaking Change (fix or feature that would cause existing functionality to not work as expected)

Further comments

This is a minimal 2-line fix. An alternative approach would be to use a combination of id and title, but since id already provides uniqueness, adding title is redundant.

Related Issue

No existing issue — found during personal use.