fix(skills): the diff skill drops its coverage ledger instructions when the coverage tools are off

strix/skills/scan_modes/diff.md

@@ -1,6 +1,7 @@
 ---
 name: diff
 description: Methodology for diff-scoped review of a pull request, commit, or branch — what counts as in scope, how far to follow a change, and what not to report
+template: jinja
 ---
 
 # Diff-Scoped Review
@@ -69,9 +70,14 @@ When it is not, the closure rules apply unchanged: a complete
 source → control → sink → impact trace through the changed code is
 reportable at reduced confidence, with the missing runtime proof named in
 `confidence_rationale`. A candidate you can neither confirm nor rule out
+{% if coverage_tools %}
 with a named control is an `open_proof_gap` — record it as
 `needs_follow_up` coverage rather than dropping it because the
 environment was inconvenient.
+{% else %}
+with a named control is an `open_proof_gap` — carry it up as an open
+item rather than dropping it because the environment was inconvenient.
+{% endif %}
 
 ## Reporting
 
@@ -80,7 +86,9 @@ plainly which part of the diff introduced or exposed it. A reviewer
 reading your report next to the diff should be able to see the connection
 without re-deriving your analysis.
 
+{% if coverage_tools %}
 Record coverage per changed component, not per changed file — a
 formatting-only file and a rewritten auth module are not equal rows.
+{% endif %}
 State which changed areas you reviewed and cleared, so the author knows
 what a clean result actually covered.

tests/test_agent_tool_registration.py

@@ -127,6 +127,13 @@ def test_coverage_tools_can_be_turned_off() -> None:
             assert "Coverage reconciliation" not in off_descriptions
         assert not any(name in off_descriptions for name in coverage)
 
+    diff_on = factory.build_strix_agent(is_root=True, is_diff_scoped=True)
+    diff_off = factory.build_strix_agent(is_root=True, is_diff_scoped=True, coverage_tools=False)
+    assert isinstance(diff_on.instructions, str)
+    assert isinstance(diff_off.instructions, str)
+    assert "Record coverage per changed component" in diff_on.instructions
+    assert "coverage" not in diff_off.instructions.lower()
+
 
 def test_instructions_override_is_used_verbatim() -> None:
     custom = "You are a scan agent. Follow the provided scope."