Refactor and optimize zine thumbnail handling:

[iUnstable0]

• Restrict thumbnail refresh to projects with existing covers.
• Adjust RefreshStaleUnifiedThumbnailsJob for efficiency.
• Prevent unnecessary scan triggers on repo_link changes or clears.
• Add targeted tests for thumbnail purge and scan workflows.
• Streamline ShipCheckService and UnifiedScreenshotFinder to improve caching and configuration flexibility.
• Sync package-lock.json to reflect updated peer and dev dependencies.

[Copilot]

Pull request overview

This PR refactors the unified thumbnail (“zine cover”) pipeline to avoid blind GitHub scans, add an owner-triggered refresh flow, and tighten caching so covers update when they exist without wasting work when they don’t.

Changes:

• Stop auto-enqueueing cover scans on project create/undiscard/repo_link edits; instead purge stale covers on repo changes and discover zines on demand / preflight / ship.
• Add owner-triggered cover refresh endpoints + frontend polling UI, with Rack::Attack throttling and Pundit gating.
• Improve finder caching semantics (skip_nil, allow_representative-aware keys) and restrict stale-refresh sweeps to projects that already have an attached cover; update and extend tests/docs accordingly.

Reviewed changes

Copilot reviewed 19 out of 20 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
test/models/project_test.rb	Updates expectations around repo_link changes (no scan; synchronous purge).
test/jobs/refresh_stale_unified_thumbnails_job_test.rb	Ensures the stale refresher only enqueues for projects that already have a cover.
test/jobs/compute_project_unified_thumbnail_job_test.rb	Aligns test stubs with updated finder signature and new enqueue behavior.
package-lock.json	Syncs dependency lockfile changes (Tailwind/oxide wasm subtree).
db/seeds.rb	Reworks dev seed demo data to use “realistic” repos/covers via the unified screenshot pipeline.
config/routes.rb	Adds refresh_cover and cover_status member routes for projects.
config/initializers/rack_attack.rb	Adds a throttle for owner-triggered cover refresh scans.
app/services/ship_checks/unified_screenshot_finder.rb	Adds cache keying by representative-allowance, skip_nil, and a force cache-bust option.
app/services/ship_checks/safe_http.rb	Prefers IPv4 for pinned-IP SSRF-safe HTTP to avoid IPv6 routing failures.
app/services/ship_check_service.rb	Adds return_context: option so callers can reuse SharedContext (preflight optimization).
app/policies/project_policy.rb	Introduces refresh_cover? authorization for the new owner-only flow.
app/models/project.rb	Replaces auto-scan callback with synchronous cover purge on repo_link changes.
app/jobs/ship_preflight_job.rb	Reuses preflight context to enqueue cover refresh when HasZinePage passes.
app/jobs/refresh_stale_unified_thumbnails_job.rb	Restricts refresh sweep to projects that already have a unified_thumbnail attached.
app/jobs/compute_project_unified_thumbnail_job.rb	Accepts source_url/force/allow_representative and adjusts concurrency key arity for new args.
app/frontend/pages/projects/show.tsx	Adds “Check for my zine” UI + polling state machine for cover refresh.
app/controllers/projects_controller.rb	Implements refresh_cover + cover_status JSON endpoints and exposes permission to the frontend.
agents-docs/arch-services-infra.md	Documents updated finder signature, caching, and force/representative behavior.
agents-docs/arch-projects-journals.md	Updates unified_thumbnail refresh contract documentation (needs a small correction).
agents-docs/arch-explore.md	Updates unified_thumbnail refresh contract documentation (needs a small correction).