core/tools: restrict edit_lineno to lines read with line numbers

tests/test_tools/test_edit_lineno.py

@@ -22,6 +22,36 @@ def test_edit_lineno_replace_middle(workspace: object) -> None:
     assert call_sync(read_file, "a.txt") == "one\nTWO\nTHREE\nfour\n"
 
 
+def test_edit_lineno_requires_all_lines_read(workspace: object) -> None:
+    del workspace
+    _ = call_sync(write_file, "r.txt", "a\nb\nc\nd\ne\n")
+    _ = reset_lineno_tracker()
+    # Only lines 2-4 are read; editing line 1 or 5 must be rejected.
+    _ = call_sync(read_file, "r.txt", offset=1, limit=3, with_lineno=True)
+    out = call_sync(edit_lineno, "r.txt", 1, 2, "X\n")
+    assert "not read" in out and "1" in out
+    out = call_sync(edit_lineno, "r.txt", 4, 5, "Y\n")
+    assert "not read" in out and "5" in out
+    # Fully read range still edits.
+    out = call_sync(edit_lineno, "r.txt", 2, 3, "B\nC\n")
+    assert "replaced lines 2-3" in out
+
+
+def test_edit_lineno_append_requires_last_line_read(workspace: object) -> None:
+    del workspace
+    _ = call_sync(write_file, "ap.txt", "a\nb\nc\n")
+    _ = reset_lineno_tracker()
+    # Only lines 1-2 read; appending after line 3 requires line 3 read.
+    _ = call_sync(read_file, "ap.txt", offset=0, limit=2, with_lineno=True)
+    out = call_sync(edit_lineno, "ap.txt", 4, 4, "d\n")
+    assert "not read" in out and "3" in out
+    # Read the last line, then append succeeds.
+    _ = call_sync(read_file, "ap.txt", offset=2, limit=1, with_lineno=True)
+    out = call_sync(edit_lineno, "ap.txt", 4, 4, "d\n")
+    assert "appended" in out
+    assert call_sync(read_file, "ap.txt") == "a\nb\nc\nd\n"
+
+
 def test_edit_lineno_delete_range(workspace: object) -> None:
     del workspace
     _ = call_sync(write_file, "b.txt", "a\nb\nc\n")