v4.3.16

Fixed

• Windows CI failure introduced by v4.3.15's zed regression test — test_zed_install_preserves_existing_config seeded AppData/Roaming/Zed/settings.json on Windows, but zed_config_dir actually uses .config/zed/settings.json on every non-macOS platform (Linux and Windows). The hand-written #[cfg(target_os = "windows")] branch in the test silently diverged from the production helper, so the test wrote the seed to one path and the install wrote to another — backup never appeared at the seeded location and the test failed.

Changed

• AgentIntegration::primary_config_path(home) -> Option<PathBuf> — new trait method that returns the single config file the integration rewrites on install/uninstall. Every agent that goes through safe_write_json_file or write_toml_file implements it (claude, gemini, cursor, opencode, zed, cline, roo-code, copilot, kilo, antigravity, codex); vibe leaves the default None because its TOML config is append-only and has no rewrite path. Regression tests in tests/agent_test.rs now call agent.primary_config_path(home) instead of duplicating platform-conditional path logic — the production helper is the single source of truth, so a future zed_config_dir-style change can't drift between tests and reality. A meta-test (test_every_tested_agent_advertises_primary_config_path) walks every integration covered by the install regression suite and asserts the method returns Some(path) under the test home, so a new integration added without wiring it up fails fast with a clear message instead of a confusing missing-backup panic later.