e2e: set detail page spec (voting, notes, social links)

[chiptus]

This was generated by AI during triage.

Slice of the e2e coverage epic #106, following the pattern proven by #111 (voting spec, PR #150).

Goal

Playwright e2e spec for the set detail page, against the local-Supabase harness.

Behaviors to cover

• Navigating to a seeded set's detail page shows its metadata (name, day/time, stage, genres).
• Voting from the detail page works and stays in sync with the vote shown elsewhere (light overlap with e2e: voting flow spec (must-go / interested / won't-go) #111 is fine — assert from this surface only).
• A signed-in group member can add a note and it appears; the note is visible to another member and not to a non-member (assert the negative where cheap).
• Social/streaming links render and point at the seeded URLs (assert hrefs, don't follow them).
• Untimed sets render without a time row (no crash, no empty artifacts).

Harness & preconditions

• Build on existing Playwright setup and TestHelpers; minimal data-testid additions only where needed.
• Seed must provide a set with social links and a group with two members for the notes assertions; extend supabase/seed.sql as needed — no production-synced data.

Verification

• pnpm run test:setup then pnpm run test:e2e green locally; deterministic across repeated runs.

Out of scope

Groups lifecycle, schedule/reveal, admin — separate slices under #106.