test(watcher): a re-synced unchanged note is not extracted twice; a changed one is (#205 S6)

Mutation-checked against the source-hash drift check.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

ingestion/internal/watcher/watcher_wing_test.go

@@ -161,3 +161,33 @@ func TestProcessDir_AProposalReasonCannotForgeFrontmatterKeys(t *testing.T) {
 	assert.NotContains(t, string(parked), "\norigin: trusted", "no injected key at line start")
 	assert.NotContains(t, string(parked), "\nwing: homelab")
 }
+
+// Syncthing can bring a removed note back (an offline peer, a restored backup).
+// The source-hash drift check must keep that from costing a second extraction.
+func TestProcessDir_ANoteThatReappearsUnchangedIsNotExtractedAgain(t *testing.T) {
+	var llmCalls atomic.Int32
+	cfg, brainDir := wingTestCfg(t, wingResolver(&stubClassifier{}, stubScorer{}), &llmCalls)
+
+	put(t, brainDir, "radar/talk.md", "The same talk, byte for byte.")
+	require.Empty(t, processDir(context.Background(), cfg, "2026-10-20"))
+	require.Equal(t, int32(1), llmCalls.Load(), "positive control: the first drop is extracted")
+	require.False(t, has(brainDir, "raw/radar/talk.md"))
+
+	put(t, brainDir, "radar/talk.md", "The same talk, byte for byte.") // the peer sends it back
+	require.Empty(t, processDir(context.Background(), cfg, "2026-10-21"))
+
+	assert.Equal(t, int32(1), llmCalls.Load(), "an unchanged source is not extracted twice")
+	assert.False(t, has(brainDir, "raw/radar/talk.md"), "and inbox zero still holds")
+}
+
+func TestProcessDir_ANoteThatReappearsChangedIsExtractedAgain(t *testing.T) {
+	var llmCalls atomic.Int32
+	cfg, brainDir := wingTestCfg(t, wingResolver(&stubClassifier{}, stubScorer{}), &llmCalls)
+
+	put(t, brainDir, "radar/talk.md", "Version one.")
+	require.Empty(t, processDir(context.Background(), cfg, "2026-10-20"))
+	put(t, brainDir, "radar/talk.md", "Version two, edited.")
+	require.Empty(t, processDir(context.Background(), cfg, "2026-10-21"))
+
+	assert.Equal(t, int32(2), llmCalls.Load(), "a real edit must still be picked up")
+}