Clarify EasyCom boundary prelabel taxonomy

docs/easycom_event_review_tool.md

@@ -164,7 +164,7 @@ non-backchannel overlap after which the wearer demonstrably holds or resumes
 the floor, and finally another interpretable overlap that fails to become a
 sustained takeover. `OTHER_HARD_NEGATIVE` is reserved for valid false-positive
 opportunities outside these named behaviors; it is never an uncertainty
-fallback. Prompt v15 gives adjacency-pair completion priority over duration:
+fallback. Prompt v16 gives adjacency-pair completion priority over duration:
 a short but complete answer to an addressed question remains a positive wearer
 entry, and floor entry does not require the wearer to retain the next turn.
 Later resumption by the questioner or another speaker therefore does not turn
@@ -173,6 +173,15 @@ reserved for feedback that does not answer a question, accept or reject a
 proposal, provide requested information, or otherwise complete an adjacency
 pair.
 
+The onset and offset of one wearer vocalization remain separate raw boundary
+candidates, but they are not automatically two scoring opportunities. If the
+wearer activity run is a backchannel inside a non-wearer's retained turn, its
+onset may be retained once as `ENTRY_WEARER_BACKCHANNEL`; its trailing offset
+is excluded as `OUT_OF_SCOPE_WEARER_BACKCHANNEL_OFFSET`, rather than being
+counted again as an INT hard negative. This episode-level interpretation is
+made by the LLM and human reviewer from timing and transcript evidence, not by
+candidate-generation gating.
+
 During live adjudication, the CLI displays a dependency-free progress bar over
 all candidate/pass work, including the current pass, batch, percentage, and
 elapsed time. Redirected logs emit periodic progress lines instead of carriage