[Parked] Source/Consumer block relationship — reference branch for Jared

[dconnenc]

Status: Draft, parked

This branch is a fully-working implementation of a Source/Consumer block model. It's pushed as a draft for context, not for merging. The simpler parent/child + flatten approach lives in #173 (block-lifecycle-decouple) — that's the one to review for the immediate need.

I'm posting this branch as reference in case the parent/child approach turns out to be limiting later, or to inform whatever direction GuessWho's overhaul takes.

Context (for @jared)

You mentioned that the original codebase had a graph-style model (variables + bindings) that you intentionally simplified down to parent/child because the upkeep wasn't paying off. When I came in not knowing that history, my first instinct was to build a Source/Consumer model — essentially the same direction you'd already moved away from.

After you flagged this, we changed course: I parked this branch and took your suggested path — try parent/child + ordering first, and only revisit the heavier model if friction shows up. That work is in #173.

The original requirements from the user were:

1. Broadcast FamilyFeud questions earlier in the experience (independent of when FamilyFeud itself runs)
2. Allow GuessWho to consume the same questions/answers

Requirement 1 is met by the parent/child + lifecycle-decouple approach in #173. Requirement 2 is already satisfied today through GuessWho's existing slides[].block_id payload references and ParticipantSubmissions.for_user, which query all blocks regardless of nesting.

What this branch contains

If we ever need cross-consumer reuse of source blocks (one Poll feeding both a FamilyFeud and a GuessWho simultaneously, surfaced in the UI), this branch has a working implementation:

Schema

• Adds source to the block_link_relationship enum on ExperienceBlockLink
• Drops the global unique constraint on child_block_id so a block can be linked from multiple consumers
• Adds position for ordering within a consumer

Backend

• New sources/consumers associations on ExperienceBlock (scoped to the source relationship; existing children/parents stay scoped to depends_on)
• Orchestrator#attach_source!, #detach_source!, #reorder_sources! endpoints under /blocks/:id/sources
• start_family_feud_playing! reads from block.sources rather than block.child_blocks

Frontend

• Core/SourcesPanel — pure presentational component with attach/detach/reorder, plus Storybook stories
• useBlockSources hook
• Wired into EditBlock for FamilyFeud — host can attach Question/Poll blocks as sources

Tests

• 344 specs pass on this branch (the snapshot when I pushed); tsc + storybook clean

When this might be worth revisiting

• GuessWho overhaul lands and needs explicit "use these specific questions as sources" semantics
• A new block kind needs many-to-many fan-in (multiple consumers reading from the same source)
• Visual UI for "which blocks does this consumer depend on" becomes a user-facing requirement

For now, the simpler change in #173 is the recommended path.

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