fix: Go to Artist shows 400 error for home page items

[sozercan]

Problem

Right-clicking items in "Listen Again" (and similar home sections) and selecting "Go to Artist" navigates to a non-existent artist page, resulting in a 400 Server Error.

Root Cause

Home page items (musicTwoRowItemRenderer) have subtitle runs with no navigationEndpoint per artist — all artists are a single comma-separated string:

"subtitle": { "runs": [{ "text": "Taylor Swift, Justin Bieber, ..." }] }

ParsingHelpers.extractArtists() generates a SHA256 hash ID for these (e.g., "a1b2c3d4e5f6..."). The old hasNavigableId check (!id.contains("-")) passed for these hex strings, but they are not valid YouTube Music channel IDs — causing a 400 when the API is called.

Confirmed via api-explorer.swift browse FEmusic_home -v — subtitle runs in home carousel items have hasNav=false, browseId="".

Fix

File	Change
Core/Models/Artist.swift	hasNavigableId now checks id.hasPrefix("UC") instead of !id.contains("-")
Views/macOS/HomeView.swift	Use hasNavigableId + first(where:) (consistent with other views)
Views/macOS/SharedViews/FavoritesSection.swift	Same inline check replaced with hasNavigableId
Core/Services/ShareService.swift	Simplified redundant guard (UC prefix check is sufficient)
Tests/KasetTests/ModelTests.swift	4 new tests: UC IDs, hash IDs, UUIDs, empty IDs
docs/common-bug-patterns.md	New anti-pattern: "Treating Generated IDs as Navigable API IDs"

Testing

• All 566 unit tests pass
• Build succeeds
• swiftlint --strict: 0 violations
• swiftformat: 0 files reformatted

[Copilot]

Pull request overview

This PR fixes a bug where clicking "Go to Artist" on home page items resulted in 400 errors. The root cause was that home page items without navigation endpoints generate SHA256 hash IDs, which were incorrectly passing the old validation check (!id.contains("-")). The fix updates the validation to explicitly check for the "UC" prefix that all valid YouTube channel IDs have.

Changes:

• Updated Artist.hasNavigableId to use id.hasPrefix("UC") instead of !id.contains("-")
• Updated HomeView and FavoritesSection to use the hasNavigableId property with first(where:) pattern
• Simplified ShareService guard by removing redundant hyphen check
• Added comprehensive test coverage and documentation

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
Core/Models/Artist.swift	Changed hasNavigableId from hyphen check to UC prefix check
Views/macOS/HomeView.swift	Uses hasNavigableId with first(where:) for consistent artist filtering
Views/macOS/SharedViews/FavoritesSection.swift	Same pattern as HomeView for consistency
Core/Services/ShareService.swift	Simplified guard to only check UC prefix
Tests/KasetTests/ModelTests.swift	Added 4 tests covering UC IDs, hash IDs, UUIDs, and empty strings
docs/common-bug-patterns.md	Documented the anti-pattern with clear examples

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.