IMPROVE: Performance pass

[merefield]

Summary

This PR is a focused performance hardening pass for discourse-workflow (9 commits, 28 files, +749/-363).

Key Changes

• Reworked /workflow quick-filtering to stay SQL-native (no Ruby-side topic_id materialization/intersection).
• Scoped charts loading to the selected workflow instead of preloading all enabled workflows.
• Reduced transition action round-trips by resolving step-option/target-step from preloaded associations and passing actor objects directly.
• Optimized daily stats persistence to set-based writes (group + bulk insert) with a unique daily bucket index on workflow_stats.
• Added workflow_states.updated_at index to support overdue/staleness filtering efficiently.
• Hardened admin payload paths against N+1 (workflows/steps/options/category preloading) and optimized workflow validation warning query patterns.
• Added/updated request+lib specs for these performance paths (including schema/index assertions and SQL-shape guards).
• UX: stop chart lines at current day when future stats are unavailable
• Updated README roadmap performance status and bumped plugin version to 0.4.1.

[Copilot]

Pull request overview

Performance-focused hardening pass for the discourse-workflow plugin, primarily targeting query shape (avoid Ruby-side ID materialization), N+1 avoidance in admin payloads, and more efficient daily stats persistence.

Changes:

• Reworked workflow list quick-filters to remain SQL-native and added regression specs guarding against topic_id plucks.
• Scoped charts payload loading to the selected workflow and added query-shape request specs.
• Reduced N+1s in admin controllers/serializers via explicit preloading, and optimized daily stats writes with set-based aggregation + bulk insert plus new supporting indexes.

Reviewed changes

Copilot reviewed 28 out of 28 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
spec/requests/workflow_list_filters_spec.rb	Adds SQL-shape guard ensuring quick-filter composition doesn’t pluck workflow_state topic IDs.
spec/requests/workflow_charts_controller_spec.rb	Adds query assertions to ensure chart loading is scoped to the selected workflow.
spec/requests/admin/workflows_controller_spec.rb	Adds query-count regression coverage for admin workflows index serialization.
spec/requests/admin/workflow_steps_controller_spec.rb	New request spec guarding against per-step queries when listing steps.
spec/requests/admin/workflow_step_options_controller_spec.rb	Adds query-count regression coverage for step option listing.
spec/lib/workflow_state_schema_spec.rb	New schema/index assertion for workflow_states.updated_at.
spec/lib/transition_spec.rb	Expands transition specs and adds a guard against per-transition target-step lookups.
spec/lib/post_notification_handler_spec.rb	Adds a bulk-loading regression check as watcher counts grow.
plugin.rb	Adds cached TopicList#has_workflow_topics? and bumps plugin version to 0.4.1.
lib/discourse_workflow/transition.rb	Refactors transition execution to use preloaded associations and accept actor objects.
lib/discourse_workflow/topic_query_extension.rb	Minor join formatting change (no behavioral change expected).
lib/discourse_workflow/stats.rb	Replaces per-row stats updates with grouped counts + insert_all! rebuild strategy.
lib/discourse_workflow/post_notification_handler.rb	Avoids per-watcher user lookups by writing notifications via user_id.
lib/discourse_workflow/list_controller_extension.rb	Converts list filtering to SQL-scoped subqueries and avoids Ruby set intersections.
db/migrate/20260223140000_add_updated_at_index_to_workflow_states.rb	Adds updated_at index for overdue/staleness filtering.
db/migrate/20260223130000_add_unique_daily_bucket_index_to_workflow_stats.rb	Adds unique daily bucket index to support set-based stats writes.
app/serializers/discourse_workflow/workflow_step_serializer.rb	Switches category serialization to a lighter serializer and uses association directly.
app/serializers/discourse_workflow/workflow_serializer.rb	Avoids repeated DB ordering/count calls by sorting preloaded steps once.
app/serializers/discourse_workflow/workflow_category_serializer.rb	New lightweight category serializer for workflow admin payloads.
app/models/discourse_workflow/workflow_state.rb	String style + schema comment update to reflect new index.
app/models/discourse_workflow/workflow_stat.rb	String style + schema comment update to reflect new unique index.
app/models/discourse_workflow/workflow.rb	Refactors validation warnings / kanban compatibility checks to reduce query churn.
app/controllers/discourse_workflow/workflow_charts_controller.rb	Loads only the selected workflow (with steps/categories) for charts.
app/controllers/discourse_workflow/workflow_action_controller.rb	Passes actor object into Transition to reduce lookup round-trips.
app/controllers/discourse_workflow/admin/workflows_controller.rb	Preloads nested associations to avoid per-workflow queries in index payload.
app/controllers/discourse_workflow/admin/workflow_steps_controller.rb	Preloads step associations for index payload (but currently contains a syntax issue).
app/controllers/discourse_workflow/admin/workflow_step_options_controller.rb	Preloads option associations for index payload (but currently contains a syntax issue).
README.md	Updates roadmap performance status items to reflect implemented work and follow-ups.

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