just mutants-gui: also the view-model oracle and copy tests

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX

justfile

@@ -96,13 +96,13 @@ mutants-mcp:
 
 # Mutation testing of the viewer where it matters: the numbers it shows
 # (the view model) and how it writes them (formatting), against the tests
-# that check them (the unit tests and spec_gui). Its read-only promise has
+# that check them (the unit tests, spec_gui, view_model, copy). Its read-only promise has
 # its own test (tests/read_only.rs, which renders every page: too slow to
 # rerun per mutant); search, history, ticks, and the attention list are
 # spec-tested, not swept.
 mutants-gui:
     mkdir -p {{mutants_tmp}}
-    PROPTEST_MAX_SHRINK_ITERS=0 TMPDIR={{mutants_tmp}} cargo mutants -p ledger-gui --test-package ledger-gui -j 4 --timeout 300 -o mutants-gui -f crates/ledger-gui/src/books.rs -f crates/ledger-gui/src/fmt.rs -- --lib --test spec_gui
+    PROPTEST_MAX_SHRINK_ITERS=0 TMPDIR={{mutants_tmp}} cargo mutants -p ledger-gui --test-package ledger-gui -j 4 --timeout 300 -o mutants-gui -f crates/ledger-gui/src/books.rs -f crates/ledger-gui/src/fmt.rs -- --lib --test spec_gui --test view_model --test copy
 
 # Benchmarks of the core's hot paths (no budget gates them yet)
 bench: