fix: multilingual URL rendering with uglyURLs

[xingzihai]

This PR fixes multilingual URL rendering when uglyURLs is enabled.\n\n## Changes\n- Fixed URL rendering to properly handle multilingual sites with uglyURLs\n\nFixes #14576

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[jmooring]

This PR does not address this comment:
#14576 (comment)

If we decide on a partial fix to close #14576, we must create a new issue to cover the multihost scenario.

I also think that we may want to address #13346 concurrently.

[Qodo-Free-For-OSS]

Hi, renderDefaultSiteRedirect skips creating a redirect for the directory containing the home output whenever the homeLink filename starts with of.BaseName + ".". Alias publishing always writes redirects to index.html for directory aliases, so this skip can incorrectly suppress redirects when the home page is written to a different filename (e.g., index.b via custom HTML suffix), where no overwrite/collision would occur.

Severity: remediation recommended | Category: correctness

How to fix: Skip only on real collision

Agent prompt to fix - you can give this to your LLM of choice:

Issue description

renderDefaultSiteRedirect currently decides whether to skip generating the alias for the directory containing the home output by checking if the last path segment of homeLink looks like an index file (HasPrefix(last, of.BaseName + ".")). This is only a proxy for the real problem (alias target overwriting the home page) and can be wrong when the home page’s output filename is not index.html.

Issue Context

• Alias publishing resolves directory aliases to .../index.html via targetPathAlias, independent of output format suffix/baseName.
• Home output filenames can vary with custom media type suffixes / output format configuration.

Fix Focus Areas

• hugolib/site_render.go[369-383]
• hugolib/alias.go[123-187]

Suggested approach

Instead of checking the link string, compute whether the would-be alias publish path would resolve to the same target file as the home page:

1. Compute the home page target filename (e.g., home.pageOutput.targetPaths().TargetFilename).
2. Compute the alias target filename for the directory alias you are about to add (use the same logic as publishing, e.g., call/replicate targetPathAlias on the alias path).
3. Only skip the last directory alias when aliasTargetFilename == homeTargetFilename.
   This keeps the current fix for /en/index.html overwrites while not disabling redirects unnecessarily for custom suffix/baseName setups.

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Found by Qodo code review. FYI, Qodo is free for open-source.