KSM-841: fix delete() skipping keys with falsy values in Oracle storage

[stas-schaller]

Summary

Fix OciKeyValueStore.delete() silently skipping deletion when a key holds a falsy value ("", 0, false).

Root Cause

delete() used if (config[key]) (truthy check) instead of if (key in config) (existence check). Keys with falsy values routed into the else branch — the key was never removed and the logger incorrectly reported "Key not found".

Same bug was fixed in Azure (KSM-835), AWS (KSM-839), and GCP (KSM-840). contains() was already corrected for Oracle in KSM-838.

Changes

• sdk/javascript/packages/oracle/src/OracleKeyValueStore.ts: Replace if (config[key]) → if (key in config) (line 433)
• sdk/javascript/packages/oracle/test/OracleKeyValueStore.test.ts: Add describe('delete() — KSM-841 regression') with 3 tests (empty string, zero, truly missing key)

Test Plan

cd sdk/javascript/packages/oracle
npm test
# Expected: 45 tests pass (3 new KSM-841 regression tests + 42 existing)

Regression tests confirmed failing before fix, passing after fix.

Closes https://keeper.atlassian.net/browse/KSM-841