Reject stale history detail actions at their shared owner

[trissim]

Recorded defect and owner correction

close-lifecycle9646's installed core-route-counts sidebar drag exited with WorkerFailed: toggle_details(None) then AttributeError("'NoneType' object has no attribute 'shown'"). Original evidence: /home/ts/.cache/agent-scratch/toad-sidebar-drag-9579/crash-frame-09.png and /home/ts/.local/state/toad/logs/Terminal_crash_2026-10-15T17_55_22_859550.txt.

LineHistory.toggle_details is now the synchronous optional-target admission boundary. Missing, retired/non-drawable, and no-longer-drawn targets schedule no work. A valid target keeps its activated top, then schedules the existing _show. Pointer activation and both keyboard expand/collapse callers share that owner; their separate worker scheduling is deleted. No new has_details policy and no independent caller checks.

The existing post-await drawable-state check and render-request source/context/width/theme checks remain. No changes to resize-owned _publish, hold_lines, or hold; no paging hunks. Published source723ff33d, separate from #675 throughput work.

Actual verification, with its limit

The real saved-thread application with source imports and installed f448/Coref1b33 dependencies survived valid tool expansion and repeated clicks/resizes, with readable history retained. Captures in /home/ts/.cache/agent-scratch/ux-held-pageup-9656/details/. The exact stale-click interleaving was not reproduced. The source boundary directly handles the recorded None failure; ordinary live survival is not proof of recreating that race.

Canonical Package/Repository AST evidence: Toad282 modules/1383 classes; installed Core321 atf1b33c10, Textual250 at17a3183b8; zero omissions. The earlier Textual254 figure described a separate Forms checkout, not this installed dependency. All direct consumers migrated; dynamic binding is source-qualified rather than proved by AST. Source/range/retirement relationships reviewed semantically. Ratchet: LineHistory GodClassExcess+6, optional-target ForeignAbsenceProbe+1; not ratchet0. Diff/AST checks passed. No automated Toad tests, synthetic application, fake provider, new input/fork, build or installation. Frontend closed normally.

Ready for independent integration review; not merged/installed and no installed-recovery claim. #675 remains draft/unaccepted for held-PageUp throughput and must not hold this recorded crash correction.

[trissim]

Owner: agent-comms-ux (existing implementation/verification owner); Codex integrates/installs. Read the complete diff against current main e8716b9: still needed, not merged or installed. Main still schedules toggle_details(None) and dereferences fragment.shown; this branch moves optional/current-target admission and worker scheduling into LineHistory, deleting the three caller scheduling decisions. Keep separate from #675 throughput. Remaining acceptance: integrated installed stale-target rejection plus valid pointer/keyboard expansion; original blocked goal/UNKNOWN inputs are unchanged.