test: stop the suite flaking on real-git and real-PTY fixtures

`npm test` was failing 5-11 tests per run with the set shifting between runs,
which made it useless as a gate. Two independent causes, neither of them a
product defect.

1. Fixtures had outgrown vitest's 5 s default. The git ones spawn 6-12
   sequential `git` processes (init/config/commit/clone/push); the real-server
   ones boot a server and a shell. Alone they finish easily; under a full
   parallel run they do not, and the failure reads `Test timed out in 5000ms`.
   Gave those describes an explicit 30 s ceiling, and the real-PTY waits a
   named PTY_WAIT_MS. The deliberate short bounds in the "must be rejected"
   handshake tests are left alone — there a timeout IS the assertion.
   (The same rebudgeting also touched the test files in the preceding commit.)

2. test/integration/server.test.ts cannot share the machine with the rest of
   the suite. It asserts on real prompt output within seconds, which is not
   achievable while ~8 workers saturate the box: it passed alone (27/27,
   repeatedly) and flaked in the full run. Raising the numbers further only
   moved the flake around, so this is fixed as a scheduling problem — `npm
   test` now runs two passes, `test:unit` (everything else, parallel) then
   `test:e2e` (that file on its own). `vitest run` still runs everything at
   once for anyone who wants that.

Also bounded the srv.close() in H1's finally. Unbounded, it swallowed whatever
really went wrong in the body — the inner waits threw, control jumped to the
finally, close() blocked, and the case reported a bare timeout instead of its
own diagnosis. The root-causing above only became possible after making that
failure legible.

Note on the `[needs real PTY (sandbox-off)]` labels: those cases were NOT
skipping here. PTY_AVAILABLE is true on this machine, so they were running and
failing on timing, not being gated out by a sandbox.

Verified: npm test green end to end across repeated runs (unit 78 files /
2147 tests, e2e 27).

package.json

@@ -15,7 +15,9 @@
     "build:web": "esbuild public/main.ts --bundle --format=esm --outdir=public/build --sourcemap",
     "dev:web": "esbuild public/main.ts --bundle --format=esm --outdir=public/build --sourcemap --watch",
     "typecheck": "tsc -p tsconfig.json --noEmit && tsc -p tsconfig.web.json",
-    "test": "vitest run",
+    "test": "npm run test:unit && npm run test:e2e",
+    "test:unit": "vitest run --exclude test/integration/server.test.ts",
+    "test:e2e": "vitest run test/integration/server.test.ts",
     "test:watch": "vitest",
     "setup-hooks": "node scripts/setup-hooks.mjs"
   },