CI: one test binary per crate, nextest, line tables only (#3855)

* CI: line tables only for workspace crates, no debug info for dependencies

* CI: one integration-test binary per crate

Each crate's tests/*.rs files become modules of tests/it/main.rs. Files that change
process-wide state (Color Settings, the font database, installed plug-ins, the working
directory), the fuzz sweeps and the test targets the Affinity corpus workflow names stay
their own binaries.

* Docs: name the integration tests' new paths

* CI: xtask test with nextest and doctests, one wasm check, clippy --keep-going

cargo xtask ci runs the tests with cargo nextest (cargo test when it is not installed),
builds them with --lib --bins --tests, runs the doctests as their own step, and checks
the wasm crates in one cargo check --keep-going call.

apps/vectorcraft/tests/it/automation_args.rs

@@ -1,6 +1,3 @@
-// Integration tests: unwrapping and panicking on failure is fine here, unlike in shipped code (AGENTS.md › Robustness).
-#![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
-
 use std::process::{Command, Stdio};
 use std::time::{Duration, Instant};
 

apps/vectorcraft/tests/it/help.rs

@@ -1,6 +1,3 @@
-// Integration tests: unwrapping and panicking on failure is fine here, unlike in shipped code (AGENTS.md › Robustness).
-#![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
-
 //! `vectorcraft --help` prints the usage and exits before the app starts (#2110): run from a
 //! terminal, SSH or an agent's shell it used to open the window (or hang without a display).
 

apps/vectorcraft/tests/it/main.rs

@@ -0,0 +1,6 @@
+//! Integration tests: one test binary for the crate, one module per area.
+// Unwrapping and panicking on failure is fine here, unlike in shipped code (AGENTS.md › Robustness).
+#![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
+
+mod automation_args;
+mod help;