C8 · /authors "Followed only" filter (PR8)

BUILD COMPLETE — PR8 "Followed only" filter on /authors, built to doc 40 in worktree feature/authors-optimization (isolated clone DB). Commits: - 2e31f303 — Add markable_favorites (user_id, markable_type, markable_id) covering index (C8/PR8). Migration 2026_07_05_000500, online ALGORITHM=INPLACE/LOCK=NONE, mirrors C2/C6 house style. Verified: migrate ran on the isolated clone (42ms), SHOW INDEX confirms col order user_id→markable_type→markable_id. Optional-but-recommended per doc §6; not load-bearing (hot path = warm cache). - 248833c7 — Add auth-gated "Followed only" filter to /authors (C8/PR8). Files (feature commit): - app/Models/User.php — new followedRedditUserIds(): array, plucks ids off cachedFollowedRedditUsersCollection() (warm 60-min cache, doc §3.1). Null-safe, no new cache key/invalidation. - app/Livewire/RedditUserIndex.php — public bool $followed_only + $queryString ('except'=>false) + updating() cursor-reset + resetFilters(). render(): server auth gate ($this->followed_only && $user instanceof User); resolves follow-id set and whereIntegerInRaw('id', $ids) (inverts drive off the 8.8M-row table, doc §2–§3.2); empty follow set → whereRaw('1=0'); disqualifies the C6 pivot-first path when followed_only so followed ∩ location runs the small id set with location as residual EXISTS (doc §5); passes followed_only_active (gated) + followed_count to the view. - resources/views/livewire/reddit-user-index.blade.php — @auth "Following" pill (violet + heart, Row 1, mirrors Verified) + tailored "not following anyone yet" empty-state CTA (doc §4/§7.2). Used doc §7.2's explicit "Following" label. - tests/Feature/Livewire/RedditUserIndexTest.php — 4 new tests: (a) guest pill hidden + ?followed_only=1 ignored, (b) signed-in sees only follows, (c) follows-nobody empty state, (d) followed ∩ location intersects. Verification: php artisan test --filter=RedditUserIndexTest → 9 passed (36 assertions); ./vendor/bin/pint → passed; php -l clean on all 4 files. (PHPStan could not run — pre-existing phpstan.neon ignoreErrors path to a deleted ProcessLegitEmbeddingResults.php halts it; unrelated to this PR, config untouched.) Scope note: implemented the followed-users toggle ONLY. Deliberately did NOT add the reserved favorite_locations_only property/queryString plumbing (doc §7.1 reserves it, but §8/§9 scope this PR to followed-users and say "do not implement that toggle from this doc" — it needs the Location-favorites model). Leaving that wiring to C9/#255 which owns it end-to-end avoids a dead URL param. Cache-key rename left to #66 as instructed.

Child of /authors optimization epic (#239). **Depends on C1.** Build in `feature/authors-optimization` worktree. Implement **PR8** (doc 40): auth-gated `followed_only` filter on `/authors` — `User::followedRedditUserIds()` from the warm 60-min cache, then `whereIntegerInRaw('id', $ids)` (filesort over tens of rows, no pivot index needed); new top-level **"Followed"** pill + empty-state; optional `markable_favorites (user_id, markable_type, markable_id)` covering index. Note: the legacy `user_followed_reddit_users_{id}` cache-key rename is a **separate cleanup pass** (#66), NOT here. Validation (Livewire): guest never sees the pill and `?followed_only=1` is ignored; signed-in sees only followed authors; follows-nobody → empty state; followed ∩ location intersects.