#515: Preserve original _id in overwrite and delete_one on decorated factbases

[VasilevNStas]

Description

Fbe.overwrite and Fbe.delete_one use delete-and-recreate when the property already exists. On a Fbe.fb-decorated factbase, the Factbase::Pre hook assigns a fresh _id ((max _id) + 1) on every insert, and the recreation loop skipped _id because it was already set. The original _id was lost, breaking external references.

Fix

Added Fbe.unid helper that removes the _id property from the fact's internal map after the Pre hook fires but before the recreation loop runs. The loop then sees _id as nil and restores the original value from before.

Affected paths:

• Fbe.overwrite hash path (line 54-65)
• Fbe.overwrite scalar path (line 86-98)
• Fbe.delete_one (line 34-42)

Closes #515

Tests

• test_preserves_id_on_decorated_fb — scalar overwrite on Fbe.fb-decorated factbase with 3 facts
• test_preserves_id_on_decorated_fb_with_hash — hash overwrite on decorated factbase
• test_preserves_id_on_decorated_fb (delete_one) — delete_one on decorated factbase

Verification

• bundle exec rubocop — 0 offenses
• bundle exec rake test — 286 tests, 0 failures

[VasilevNStas]

@yegor256 please review

[VasilevNStas]

Closing per @yegor256 feedback: the approach needs architectural approval first. Moved discussion to #515.