docs: update replay-test skill with Worms 2D suite and generate-baseline

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude/skills/replay-test/SKILL.md

@@ -32,6 +32,7 @@ Options:
 - `.\run-tests.ps1 longbow` — filter by name
 - `.\run-tests.ps1 -j 1` — serial mode (for debugging)
 - `.\run-tests.ps1 --no-build` — skip internal DLL/launcher build (assumes already built)
+- `.\run-tests.ps1 -d testdata/replays/worms2d` — run the Worms 2D speedrun replay suite instead
 
 ## Modes
 
@@ -86,11 +87,39 @@ All are set automatically by the test runner.
 ## Key Paths
 
 - Replay files + expected logs: `testdata/replays/*.WAgame` + `*_expected.log`
+- Worms 2D speedrun replays: `testdata/replays/worms2d/*.wagame` + `*_expected.log`
 - Per-run output: `testdata/runs/<timestamp>/` (gitignored)
 - Test runner: `crates/openwa-test-runner/` (`openwa-test` binary)
 - Headless script: `run-tests.ps1`
 - Headful script: `replay-test.ps1`
 
+## Worms 2D Speedrun Replays
+
+~598 replays from the [Worms 2D file archive](https://worms2d.info/files/replays/) in `testdata/replays/worms2d/`. These cover all 33 single-player campaign missions with diverse weapon usage, schemes, and game states.
+
+```bash
+# Run the Worms 2D suite (use -j 1 or -j 2 to avoid concurrency flakes)
+openwa-test -d testdata/replays/worms2d -j 1
+```
+
+**Important:** At `-j 4` or higher, ~5-7% of tests flake with "Cannot play game file" errors due to WA.exe instances contending on shared resources not covered by file isolation hooks. Always use `-j 1` or `-j 2` for this suite. The full suite takes ~3-4 minutes at `-j 1`.
+
+**When to run:** The full Worms 2D suite is slow — use it only as final validation after complex features or refactoring, not for iterative development. The base `testdata/replays/` suite (15 tests, ~1-2s) should be run routinely.
+
+## Generating Baselines
+
+Use the `generate-baseline` subcommand to create `_expected.log` files for new replays:
+
+```bash
+# Generate baselines for all replays in a directory that don't have one yet
+openwa-test generate-baseline -d testdata/replays/worms2d -j 1
+
+# With a filter
+openwa-test generate-baseline -d testdata/replays/worms2d "wa01"
+```
+
+This runs each replay with `OPENWA_TRACE_BASELINE=1` (minimal hooks — only headless, file isolation, frame counting) and copies the output log as the expected baseline.
+
 ## Adding New Replay Tests
 
 1. Record a game in WA.exe (replay `.WAgame` saved automatically)