fix(analytics): attribute referrer to the entry page only

[raifdmueller]

Why

Follow-up to #562/#565. Now that in-app navigation is counted, the referrer breakdown over-attributed external sources: document.referrer stays fixed for the whole SPA session, so a single visitor arriving from heise and clicking through ~20 anchors made heise's referrer list show all 20 paths (mostly count 1) — even though heise only links 3-4 pages.

What

Send the referrer only on the initial load (handled by count.js). Client-side route changes now pass a referrer callback returning '', so in-app anchor/page views carry no referrer. External referrers are credited to the landing page only — matching the intuitive "where did this visit come from" meaning.

(We may revisit "full journey" attribution later — it's a nice engagement signal — but entry-only is the expected default.)

Verification (preview, GoatCounter get_data, faked document.referrer = heise)

• Landing vars → r = "https://www.heise.de" (entry credited to heise)
• SPA anchor view vars → r = "" (no referrer)

Router tests pass; lint + prettier clean.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Verfeinerte Seitenaufruf-Erfassung: Bei internen (Client-)Navigationen werden keine vorherigen Seiten mehr als Referrer weitergegeben, wodurch Analytics-Daten präziser sind. Der initiale Seitenaufruf wird weiterhin automatisch erfasst.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

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Review profile: CHILL

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Run ID: 355284e8-4000-4bdd-9823-d891155b77b4

📥 Commits

Reviewing files that changed from the base of the PR and between 7758c65 and 8baa5f9.

📒 Files selected for processing (1)

• website/src/utils/router.js

🚧 Files skipped from review as they are similar to previous changes (1)

• website/src/utils/router.js

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Walkthrough

Die trackPageview()-Funktion in website/src/utils/router.js ruft bei Client-Navigationen gc.count() nun mit einem referrer-Callback auf, das konsequent einen leeren String zurückgibt, sodass Referrer nicht zwischen In-App-Views weitergereicht werden.

Changes

GoatCounter Referrer-Handling in Client-Navigation

Layer / File(s)	Summary
trackPageview Referrer-Callback website/src/utils/router.js	Die trackPageview()-Funktion ruft gc.count() mit einem referrer-Callback auf, das für Client-seitige Routen-Navigationen einen leeren String liefert; Kommentare dokumentieren die Änderung.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• LLM-Coding/Semantic-Anchors#562: Beide PRs modifizieren website/src/utils/router.js's SPA-Tracking (trackPageview / gc.count) — eines fügt SPA/Anchor-Counting hinzu, das andere ändert den referrer-Callback.

Suggested reviewers

• JensGrote

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	Der Titel beschreibt präzise die Hauptänderung: Referrer werden nur der Einstiegsseite zugeordnet, nicht zu nachfolgenden In-App-Navigationen.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[JensGrote]

LGTM ✅

Clean fix. GoatCounter's referrer callback API is the right approach for SPA sessions — the comment explains the problem (heise inflating 20 paths) well.

One thought for the future: if you ever want "full journey" attribution (mentioned in the PR description), you could send something like referrer: () => window.location.origin + previousPath to track internal navigation chains without external referrer bleeding. But entry-only is the sane default for now.