Migrate CLI E2E tests to Node.js 26

Run the CLI subprocess suites and benchmark tools as native TypeScript with
node:test, and move them under test/e2e-cli.

Update CI and Compose runners, run local smoke tests on Linux, macOS, and
Windows, and collect source-mapped CLI coverage with c8.

test/e2e-cli/CONTRIBUTING_TESTS.md

@@ -0,0 +1,70 @@
+# Writing CLI Tests with Node.js
+
+Add CLI end-to-end tests under `test/e2e-cli/`. This suite uses Node.js 26 native TypeScript support and the built-in `node:test` runner so that local filesystem and subprocess scenarios can run on Windows, macOS, and Linux.
+
+## Principles
+
+- Keep one scenario per file when practical.
+- Reuse helpers from `helpers/` rather than duplicating process, Docker, or settings logic.
+- Prefer deterministic data over random inputs unless randomness is explicitly required.
+- Ensure every test can clean up automatically.
+- Keep assertions actionable with clear failure messages.
+- Keep test concurrency at one. Tests share the built CLI and may start local services.
+- Use TypeScript syntax which Node can strip without compilation; `test/e2e-cli/tsconfig.json` checks this boundary.
+
+## Directory structure
+
+```text
+test/e2e-cli/
+  helpers/
+    backgroundCli.ts
+    cli.ts
+    docker.ts
+    env.ts
+    p2p.ts
+    settings.ts
+    temp.ts
+  test-*.ts
+  run-task.ts
+  tasks.json
+  ci-tasks.json
+```
+
+## Test file naming and assertions
+
+Use `test-<feature>.ts`, aligned with existing CLI test names where practical. Import the built-in test and assertion APIs: `test` and `describe` from `node:test`, and assertions from `node:assert/strict`. For example:
+
+```ts
+import assert from "node:assert/strict";
+import { test } from "node:test";
+
+test("feature: behaviour", async (t) => {
+    await t.test("preserves the expected result", () => {
+        assert.equal(actualValue, expectedValue);
+    });
+});
+```
+
+## Core helper usage
+
+- `runCli(...)` and `runCliOrFail(...)` execute the CLI and return or validate its result.
+- `runCliWithInputOrFail(input, ...)` supports `put` and other stdin-driven commands.
+- `TempDir` and `await using` provide automatic temporary-directory cleanup.
+- Settings helpers create baseline files and apply CouchDB or P2P configuration.
+- Docker helpers start, initialise, and stop local CouchDB, RustFS, and relay services when a test needs them.
+- `startCliInBackground(...)` manages long-running host commands such as `p2p-host`.
+
+Prefer `try`/`finally` when a test needs explicit cleanup in addition to registered test hooks. For network-sensitive commands, use `LIVESYNC_CLI_RETRY` during debugging. Keep Docker container reuse disabled by default unless debugging.
+
+## Task registration
+
+Add each supported task name to `tasks.json`. A task record uses one of these forms:
+
+- `{ "test": ["test-file.ts"] }`, optionally with a `filter` regular expression for named subtests.
+- `{ "script": "script.ts" }` for a TypeScript script.
+- `{ "tasks": ["task-name"] }` for an ordered task group.
+- `{ "command": "...", "args": [...] }` only for the retained legacy benchmark shell scripts.
+
+Add a task name to `ci-tasks.json` only when it belongs in the standard service-backed CI suite. That file is authoritative for both `run-ci-suite.ts` and the automatic CI matrix. Keep the local `test:local` group service-free so it remains suitable for Windows, macOS, and Linux smoke runs.
+
+Use `npm run test:e2e:task --workspace self-hosted-livesync-cli -- <task-name>` from the repository root to run one task after building the CLI. The standard suite and canonical P2P suite use `npm run test:e2e:cli` and `npm run test:e2e:cli:p2p`, respectively. P2P network scenarios use Compose because host networking and WebRTC candidate selection are not reproducible across environments; individual host-direct P2P tasks are for explicit diagnostics.