fix(dedup): the two new report kinds say what to DO about a duplicate (#4164)

`_REPORT_KINDS` gained `lesson` and `process` without `_KIND_SUGGESTION`
gaining either, so the report would have listed pairs with no advice —
and the suggestion is the report's point. CI's per-kind guard caught it.

Lesson: read both triggers first (a lesson is retrieved by the situation
it names, so alike insights under different triggers are two lessons);
same trigger means one lesson learned twice, so fold the `taught_by`
union into the survivor and delete the other. Process: a process arrives
as a skill, so a duplicate runs the wrong procedure rather than merely
cluttering a list — keep the one in use, fold the missing steps, delete
the loser.

The guard now asserts the property per kind rather than spot-checking
two: no non-snippet suggestion may propose merge_snippets, so a sixth
kind inherits the bar without anyone editing the test.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

tests/test_services_dedup.py

@@ -344,6 +344,10 @@ def test_every_kind_has_a_suggestion_and_none_proposes_merging_notes():
 
     for kind in _REPORT_KINDS:
         assert _KIND_SUGGESTION.get(kind), f"no suggestion for {kind}"
+        if kind != "snippet":
+            # The property, not a spot-check: a sixth kind added to the
+            # report inherits the bar without anyone editing this test.
+            assert "merge_snippets" not in _KIND_SUGGESTION[kind]
     assert "merge" in _KIND_SUGGESTION["snippet"]
     assert "NOT merge" in _KIND_SUGGESTION["note"]
     assert "supersedes" in _KIND_SUGGESTION["note"]