Q-W2 review follow-ups: anon-namespace TU-private panel helpers, fix stale bank_panel.cpp comments, correct shim-transitivity claim

Wraps ~50 file-local helpers across all eight panel TUs in namespace{} (dissolves the menuAppend default-arg ODR trap); zero behavior change, 60/60 green.

src/shell/panel/panel_state.h

@@ -14,10 +14,12 @@
 //     plain free function — direct call-through, no interface, no virtual dispatch
 //     (T4-28: the audition path and the per-mouse-move path must stay direct calls).
 //   * Explicit using-declarations pulling the pure modules' symbols into
-//     reasampler::panel from their REAL namespace homes (Q-W1 sub-namespaces) — the
-//     panel TUs do NOT include the interim core/namespaces.h shim (Q-W2 retires it
-//     for this module; some still-unsplit shell headers carry it transitively until
-//     their own waves, but nothing here depends on it).
+//     reasampler::panel from their REAL namespace homes (Q-W1 sub-namespaces) — this
+//     header itself does not directly include the interim core/namespaces.h shim
+//     (Q-W2 retires that direct dependency for this module). Six of the eight panel
+//     TUs still pull the shim in TRANSITIVELY via actions.h/persist.h/ingest.h/
+//     draw_kit.h/view.h; only panel_thumbnails.cpp and panel_audition.cpp are
+//     shim-free end to end. Nothing HERE depends on it either way.
 //
 // REFERENCE-INVALIDATION GUARDRAIL (CONTEXT.md §Multi-bank): a bank-structural
 // mutation (create/delete/evacuate/activate/move) can reallocate the book's vector,