fix(hooks): after-write dedups its channel files; prior-art tests follow the extractor and skip list into scribe_defs.sh (#2901)

Run 4240: two pre-write hook tests pinned the skip case and scribe_defs()
inside scribe_prior_art.sh, which moved to the shared library; the after-write
test saw the same derive key appended once per changed file. Keep each token
once (sort -u after the appends) and point the pins at the library.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_write_path_trigger.py

@@ -853,14 +853,18 @@ def test_hook_exits_silently_when_unconfigured():
 
 
 def test_hook_skips_prose_and_data_files():
-    """No round-trip for a markdown edit — the server would return nothing anyway."""
-    src = HOOK.read_text()
-    skip = re.search(r"case \"\$file_path\" in\n(.*?)esac", src, re.S)
-    assert skip, "expected an extension skip list"
+    """No round-trip for a markdown edit — the server would return nothing
+    anyway. The list lives in the shared library (#2901) and the hook asks it."""
+    lib = (PLUGIN / "hooks" / "scribe_defs.sh").read_text()
+    skip = re.search(r"scribe_skip_path\(\) \{\n  case \"\$1\" in\n(.*?)esac", lib, re.S)
+    assert skip, "expected an extension skip list in scribe_defs.sh"
     for ext in ("*.md", "*.json", "*.lock", "*.png"):
         assert ext in skip.group(1)
     # Config formats are deliberately NOT skipped — a workflow file is reusable.
     assert "*.yml" not in skip.group(1)
+    src = HOOK.read_text()
+    assert 'scribe_skip_path "$file_path" && exit 0' in src
+    assert '/scribe_defs.sh"' in src                   # sourced, not copied
 
 
 def test_plugin_version_bumped_with_the_hook():
@@ -1150,7 +1154,9 @@ def test_hook_names_the_shapes_being_written():
     that changes a body, not a signature — the definition enclosing the edit,
     found by walking the target file upward from the edited lines."""
     src = HOOK.read_text()
-    assert "scribe_defs()" in src                      # one extractor, two consumers
+    lib = (PLUGIN / "hooks" / "scribe_defs.sh").read_text()
+    assert "scribe_defs()" in lib                      # one extractor, shared (#2901)
+    assert "scribe_defs()" not in src                  # ...not a second copy here
     assert ".tool_input.old_string" in src             # the Edit's anchor
     assert "| tac | scribe_defs | head -1" in src      # nearest definition above
     # The ledger feed sends NAMES, never bodies, and stays on the one GET.