app: ListingView — virtualized flat code+data listing for regions (M2)

The real disassembly-listing view. ListingView is a line-virtualized
ScrollView (reusing ColumnCursor/SearchMixin/NavMixin) backed by
ListingModel, rendering code, data (db/dw/dd, strings, jump tables) and
undefined bytes interleaved with per-kind styling. Non-function regions now
open in it instead of the M0 DisasmModel stopgap.

Integration (IdaTui): a new `listing` active mode. _open_entry routes region
entries to ListingView; _show_active/compose add it; follow/xrefs/comment and
the c/p/u edit verbs handle it (define_func upgrades a region straight to the
function view); backslash reaches hex and returns via _code_mode (so leaving
hex from a region lands back on the listing, not a func view); Tab explains
there's no pseudocode for a region. rpc._active_widget learns `listing`.

Server fix (the important one): the `heads` walker now steps by get_item_end
instead of next_head. next_head SKIPS undefined bytes, so after undefining a
function its start address wasn't even a listing line and the cursor snapped to
the next defined item; stepping by item-end renders undefined bytes as `db ?`
lines (IDA-accurate) and makes navigation land exactly on any address —
essential for "go to unmarked bytes and hit c". Needs a supervisor restart.

Tests: region_define rewritten to assert the ListingView path + segment-wide
listing + p-upgrade; new listing_view scenario (data-segment listing renders
data heads, cursor reports head ea, backslash->hex->back). Pilot 115 pass / 1
pre-existing flaky (filter); rpc_smoke 29/0; test_domain 27/0.

1 files changed, 11 insertions, 5 deletions

diff --git a/TODO b/TODO
index a1ff814..92ecfa1 100644
--- a/TODO
+++ b/TODO
@@ -17,11 +17,17 @@ hard:
 [ ] deal with PLT stubs and such (oh god here we go)
 [~] how to deal with non-function-body regions?
     -> we want to be able to do data/type definitions in .data etc.
-    -> M0 done: navigating to a non-function EA opens a flat listing (region)
-       instead of refusing; c/p/u edit verbs on the disasm view (define code /
-       function / undefine) with bump_items() cache invalidation + region->func
-       upgrade. next: M1 server `heads` walker + ListingModel (address paging),
-       M2 ListingView (code+data render), M3 data typing in .data.
+    -> M0 done: navigating to a non-function EA opens a flat listing instead of
+       refusing; c/p/u edit verbs (define code/function/undefine) with
+       bump_items() cache invalidation + region->func upgrade.
+    -> M1 done: server `heads` walker (walks item-ends so undefined bytes show
+       as `db ?` and arbitrary addresses land exactly) + ListingModel.
+    -> M2 done: ListingView — virtualized flat listing (code+data+undefined,
+       kind-styled), wired into nav/follow/xrefs/hex/edit-verbs. region views
+       now use it (not the DisasmModel stopgap).
+    -> next: M3 data typing in .data (`d`/make_data with a type prompt, struct-
+       typed data, string/dup coalescing for big undefined runs); M4 optionally
+       unify the function disasm view as a filtered listing.
 
 crazy:
 [ ] multi/split view ala ghidra?