Make agent instructions harness agnostic

.agents/skills/benchmark/SKILL.md

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+---
+name: benchmark
+description: Run and author benchmark tests in xterm.js. Use when editing benchmark files, working in `*.benchmark.ts`, or when asked how to run the full benchmark suite, a single benchmark file, or a single benchmark case.
+---
+
+# Benchmark Run Instructions
+
+## Running Benchmarks
+
+- Full suite: `npm run benchmark`
+- Single benchmark file:
+  - Tree: `npm run benchmark -- -t out-test/benchmark/Event.benchmark.js`
+  - Run file: `npm run benchmark -- -s "out-test/benchmark/Event.benchmark.js" out-test/benchmark/Event.benchmark.js`
+- Single context/case:
+  - Use `-t` to get the path, then:
+  - `npm run benchmark -- -s "<path>" out-test/benchmark/Event.benchmark.js`
+
+## Benchmark Case Selection
+
+When writing benchmark instructions:
+
+- Use `RuntimeCase` to measure pure runtime in ms.
+- Use `ThroughputRuntimeCase` when measuring throughput in MB/s.
+
+## Notes
+
+- Benchmarks run from built JS in `out-test/benchmark/*.benchmark.js`.
+- Keep `NODE_PATH=./out` (handled by the npm script).

.agents/skills/unit-test/SKILL.md

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+---
+name: unit-test
+description: Write and review xterm.js unit tests with project conventions. Use when editing `*.test.ts` files or when asked for test authoring guidelines.
+---
+
+# Unit Test Instructions
+
+When writing unit tests, follow these rules:
+
+- When writing unit tests for addons, always create a real xterm.js instance instead of mocking it.
+- Prefer `assert.ok` over `assert.notStrictEqual` when checking something is undefined or not.
+- Avoid comments as most tests should be self-documenting.