docs(graph): fix stale MemoryError::NotFound link in add_relation

[raymondj99]

Fixes the failing rustdoc CI job on main after v0.4.0 (#22). The add_relation docstring referenced MemoryError::NotFound, a non-existent variant. The real variant is MemoryError::EntityNotFound — caught in the implementation, missed in the docs.

cargo doc --workspace --no-deps and cargo doc --workspace --no-deps --all-features both clean locally after this one-character fix.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Documentation
  • Clarified documentation for relation addition functionality to accurately reflect the error type returned when unknown entity identifiers are encountered.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: dd13b53f-7d26-47a2-8843-d867a5f2fb69

📥 Commits

Reviewing files that changed from the base of the PR and between 76884c9 and fb5e649.

📒 Files selected for processing (1)

• crates/openmemory-graph/src/store.rs

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📝 Walkthrough

Walkthrough

This PR corrects the documentation for MemoryStore::add_relation to accurately reflect the actual error type returned when entity IDs are not found. The doc comment now specifies MemoryError::EntityNotFound instead of MemoryError::NotFound.

Changes

Error documentation correction

Layer / File(s)	Summary
add_relation error documentation crates/openmemory-graph/src/store.rs	Doc comment for MemoryStore::add_relation updated to document MemoryError::EntityNotFound as the error variant for unknown entity IDs.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Poem

A doc needs a fix, just one little line,
EntityNotFound—now the error shines!
No logic was harmed in this change so divine,
Just clarity blooming, documentation so fine. 🐰✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and accurately describes the main change: fixing documentation in the add_relation function by correcting a stale error type reference from MemoryError::NotFound to MemoryError::EntityNotFound.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/rustdoc-link

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[codspeed-hq]

Merging this PR will not alter performance

✅ 19 untouched benchmarks

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_{Comparing fix/rustdoc-link (fb5e649) with main (76884c9)}