fix: unpack community results from semaphore_gather in add_episode

[just-jeb]

Summary

Fixes a ValueError: not enough values to unpack (expected 2, got N) crash in add_episode when update_communities=True.

Type of Change

• Bug fix

Objective

semaphore_gather returns a list of results — one (communities, edges) tuple per coroutine (one per extracted node). The previous code tried to unpack that list directly as two variables:

communities, community_edges = await semaphore_gather(
    *[update_community(...) for node in nodes],
    max_coroutines=self.max_coroutines,
)

This raises ValueError: not enough values to unpack (expected 2, got N) for any episode that extracts at least one node, making add_episode with update_communities=True entirely broken.

Fix: collect into a results list, then flatten:

community_results = await semaphore_gather(...)
communities = [c for r in community_results for c in r[0]]
community_edges = [e for r in community_results for e in r[1]]

Testing

• Unit tests added/updated (tests/test_community_update_unpack.py)
• Integration tests added/updated
• All existing tests pass

Two unit tests:

1. test_semaphore_gather_community_results_flatten — verifies the fixed flatten logic correctly collects communities and edges across multiple nodes
2. test_semaphore_gather_unpack_raises_without_fix — demonstrates the old pattern raises ValueError, confirming the bug existed

Breaking Changes

• This PR contains breaking changes

Checklist

• Code follows project style guidelines (make lint passes)
• Self-review completed
• No secrets or sensitive information committed

Related Issues

Reproduces on graphiti-core==0.29.0. Verified fix locally.

[just-jeb]

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[danielchalef]

Maintainer note: rebased this onto current main (the fix still applies cleanly at graphiti.py:1185) and verified the regression test passes. Selecting this as the canonical fix for the update_community / semaphore_gather unpack bug — it's the most complete of the duplicates and the only one with a regression test. Closing #1421, #1254, and #1085 as superseded by this PR. Thanks!