ci: add native UI accessibility end-to-end gates

[turinglambdaai]

Summary

• drive the packaged Taskboard through UI Automation, AXUIElement, and AT-SPI on the three native desktop stacks
• assert stable semantics, one RPC/State mutation, one Event, the final large State, and orderly close
• upload bounded accessibility snapshots, interaction traces, screenshots, and native logs even when a gate fails
• document the product-level native test extension point without adding a shared UI DSL

Closes #184 after all three platform jobs are green.

Local validation

• Python AST parse and bash syntax check
• PowerShell parser validation
• workflow parsed with PyYAML
• raco test tests/documentation.rkt: 153 tests passed
• git diff --check

[turinglambdaai]

Pushed e14f6fe to address both native UI failures. Linux now explicitly enables the GTK AT-SPI backend and always captures the discovered accessibility tree. Windows now virtualizes the 1,000-row list, assigns stable AutomationIds to realized containers, closes through the native WM_CLOSE path, stops the embedded backend deterministically, and releases the last WinUI Window without forcing Application::Exit during Closed teardown. Local full UIA evidence: all interactions and assertions passed; clean process exit in 117 ms. Also verified python -m py_compile and bash -n.

[turinglambdaai]

Pushed the root-cause fix in the native harness. Windows evidence showed Process.CloseMainWindow was selecting the lazily allocated diagnostic console, leaving the real WinUI window open; the gate now posts WM_CLOSE to the exact HWND exposed by the UIA root and releases provider proxies (local full 1,000-row run exits cleanly in 106 ms). Linux evidence showed GTK/AT-SPI exposes visible control names and the live status text rather than the requested GtkAccessible label property on Ubuntu 24.04, so the gate now asserts the actual assistive-technology tree and tracks the live status object. The uploaded failing trees were used directly for both corrections.

[turinglambdaai]

The latest native-E2E evidence exposed three platform-specific lifecycle details, now fixed in 40fa499: GTK 4.14 publishes actionable controls through AT-SPI SENSITIVE without the optional ENABLED bit; Swift 6 rejects conditional casts to Core Foundation accessibility types; and WinUI desktop applications own their dispatcher independently of their final window, so the reference app now ends the application lifecycle explicitly after its earlier-registered backend shutdown handler completes. The exact-HWND UIA path and the 1,000-row interaction assertions remain unchanged.

[turinglambdaai]

Rebased by merge onto current main after #198 and #199. Local Windows verification on the merged tree passed end to end: clean package, UI Automation RPC/Event/1,000-row State assertions, native close, backend shutdown, and process exit. The test remains strict; #199 removes the inherited diagnostics console that kept the process alive in CI. Also re-ran documentation and pending/diagnostics tests: 211 passed.

[turinglambdaai]

The macOS artifact proved all AX interactions and the final 1,000-row State succeeded. The remaining failure was lifecycle-specific: SwiftUI WindowGroup kept the application resident after its last window closed, and the failure cleanup then waited without a bound after SIGTERM.

This update makes the product behavior explicit: the AppKit delegate terminates after the last window closes, the root view stops the embedded backend on disappearance, and CI cleanup escalates from TERM to KILL within ten seconds so a future lifecycle regression produces a prompt failure plus artifacts instead of a 25-minute cancellation. The successful path now emits shutdown-trace.json. Current main (#202) is merged into the branch; YAML, diff checks, and 211 documentation/backend tests pass locally.