* fix(agents): pair null call IDs with empty result IDs
* fix(agents): treat producer sentinel IDs as absent when pairing
Middleware producers spell a missing provider ID three ways: "" is canonical,
str(tool_call.get("id", "")) yields "None" once the key is present with a
null value, and the artifact/deferred/knowledge middlewares fall back to
"missing_tool_call_id". Only "" reached the pairing pass, so a result carrying
either sentinel was dropped as an orphan and the middleware's guidance was
replaced by the interrupted placeholder — the exact outcome this PR set out to
avoid, just through a different spelling.
Route every absent spelling through one canonicalisation used by the pairing
gate, the candidate comparison and the turn-completeness count.
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Co-authored-by: huyengiang101086-spec <270684046+huyengiang101086-spec@users.noreply.github.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
