fix(seo): canonicalize dotted documentation routes

[sfanahata]

DESCRIBE YOUR PR

Fixes non-indexable canonical targets for documentation routes whose final segment contains a dot, including Java and Python migration guides such as 7.x-to-8.0 and 1.x-to-2.x.

How it was fixed:

• Normal documentation pages use a trailing slash.
• Pages with filename-like version numbers, such as 7.x-to-8.0, do not.
• The home page remains /.

We then applied that same rule everywhere Sentry tells search engines about official URLs:

• The canonical tag inside each page
• The sitemap submitted to search engines
• The canonical header attached to Markdown versions of pages
• Manually configured canonical paths

This PR adds one shared canonicalPath helper that mirrors Next.js route normalization and uses it for:

• HTML canonical metadata
• Sitemap URLs
• Canonical Link headers on .md responses
• Custom canonical paths

Ordinary documentation routes continue to use trailing slashes. Dotted migration and versioned routes use the direct no-slash form.

Verification

• pnpm test:ci: 377 tests passed
• pnpm lint:eslint: 0 errors (9 existing warnings)
• pnpm lint:prettier: passed
• pnpm lint:ts: passed
• Next production compilation completed locally; the full Vercel production build passed
• Local HTTP verification confirmed:
  • Java and Python dotted routes return 200 and are self-canonical without /
  • Their slash forms return 308 to the no-slash URL
  • An ordinary docs route returns 200 and is self-canonical with /
  • Sitemap and .md canonical headers use the same route-aware forms

IS YOUR CHANGE URGENT?

• Urgent deadline (GA date, etc.)
• Other deadline
• None: Not urgent, can wait up to 1 week+

PRE-MERGE CHECKLIST

• Checked Vercel preview for correctness, including links
• PR was reviewed and approved by any necessary SMEs
• PR was reviewed and approved by a member of the Sentry docs team

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Project	Deployment	Actions	Updated
develop-docs	Ready	Preview	Sep 8, 2026 11:07pm UTC
sentry-docs	Ready	Preview	Sep 8, 2026 11:07pm UTC

[sergical]

small comment otherwise LGTM

[sergical]

why is localhost indexable?