Normalize Env subscriber path/URL payloads to UTF-8 binaries

[dominicletz]

Summary

Desktop.Env subscriber OS events (:open_url, :open_file, :print_file) now always deliver UTF-8 binaries (String.t()), whether they arrive from wx (charlists) or from native bridges (already binaries).

This closes the gap where EventBridge/notify_subscribers sent binaries while wx handle_info forwarded charlists (including a bare charlist as the second tuple element), which broke app adapters that only handled one encoding.

Changes

• Add t:subscriber_event/0 / t:os_app_event/0 / t:desktop_event/0 and document the contract on subscribe/0 and notify_subscribers/1
• Normalize path/URL lists at both ingest paths (notify_subscribers cast and OS handle_info) before buffer or delivery
• Tests for binary passthrough, charlist lists, bare charlist, pre-subscribe buffer replay, :window_activated, and :new_file
• Move wx-only Env checks to test/desktop/env_wx_test.exs so browser/normalization tests are not polluted by WxCase module setup
• Changelog under 1.6 (unreleased); fix historical 1.3 note to use list form {:open_url, [url]}

Test plan

• NO_WX=1 mix test test/desktop/env_test.exs (8 tests, 0 failures)
• NO_WX=1 mix test.fast (pre-existing unrelated failures in this environment)
• xvfb-run -a mix test.wx when a display is available

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Note

Medium Risk
Changes the on-the-wire contract for OS open events that apps handle via Env.subscribe/0; apps that matched only charlists or only binaries must align with binaries, but behavior is now consistent across wx and native paths.

Overview
Desktop.Env subscribers now always get UTF-8 binaries for :open_url, :open_file, and :print_file, fixing inconsistent charlist vs binary payloads from wx vs bridges.

Normalization runs on notify_subscribers/1 and on OS handle_info ingest (including events buffered before subscribe/0), with a special case for wx’s bare charlist second element ({:open_url, ~c"..."}). subscribe/0 and module docs document t:subscriber_event/0 and related types; other events (:new_file, :window_activated) are unchanged.

Tests cover passthrough, charlist conversion, buffering, and non-path events; wx-only Env tests move to test/desktop/env_wx_test.exs. Changelog and the 1.3 note are updated to describe list-shaped {:open_url, [url]}.

^{Reviewed by Cursor Bugbot for commit 8a3d5fa. Configure here.}