Reach 100% test coverage

[mckalexee]

Raises coverage from 93% statements / 81% branches to 100% on all four metrics (statements, branches, functions, lines). 24 new tests, 109 total. Test-only apart from a comment in lib/condition.ts; no runtime behavior changes and no version bump — this rides along with the next release.

Each test pins an observable contract through the public API rather than targeting lines:

Integration tests (facet.test.ts, against DynamoDB Local)

• get of a missing record returns null; get([]) resolves without a network call; first() on an empty partition returns null
• Raw-string sort-key arguments address the same records as the object form
• Conditions that compare stored attribute values (optimistic locking) — prior condition tests only used exists/not_exists, which never produce ExpressionAttributeValues
• validateInput: true rejects invalid writes and persists the validator's return value; the default defers validation to the read path
• Numeric TTL fields pass through as epoch seconds; unparseable TTL strings are dropped rather than stamped as NaN
• Shard placement pinned as a persistence contract: undefined shard-key values are excluded from the hash input, multi-key inputs keep the null-byte separator
• Composite keys stringify booleans/bigints and omit objects entirely; pick() without a pickValidator throws; duplicate index aliases throw; unaliased indexes work via their GSI slot

Mocked failure paths

• batch-write.test.ts: a thrown batchWriteItem fails only its own batch (26-record test, poisoned first batch, the 26th still succeeds); malformed or never-sent UnprocessedItems entries are ignored instead of crashing or mis-reporting good items
• get.test.ts: unprocessed keys are retried (only the unprocessed key is re-requested), persistent unprocessed keys keep retrying, and after 10 attempts the get returns best-effort results (fake timers — the real backoff sums to ~20s); a rejected batchGetItem propagates; an UnprocessedKeys entry without a Keys array reads as empty
• New query.test.ts: a query response with no Items field yields an empty result

The one source change

condition.ts gets a /* v8 ignore next 3 */ on the empty-names guard: every @faceteer/expression-builder operator aliases at least one attribute name, so the branch is unreachable, but the guard stays as defense against empty maps (which DynamoDB rejects).

No coverage thresholds were added to the vitest config — CI does not gate on coverage.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (da45a50) to head (f0db70d).

Additional details and impacted files

@@             Coverage Diff              @@
##             main       #59       +/-   ##
============================================
+ Coverage   87.52%   100.00%   +12.47%     
============================================
  Files          13        13               
  Lines         465       457        -8     
  Branches       92        91        -1     
============================================
+ Hits          407       457       +50     
+ Misses         32         0       -32     
+ Partials       26         0       -26     

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