test(cli): no timeout decides a cli_scope test; finish keeps the environment

[DeusData]

Follow-up to #2589, test code only (tests/test_cli.c).

What

No timeout decides a cli_scope test. #2589 removed the 90 s readiness deadline. Four other timeouts could still turn a slow but healthy run into a failure:

wait	before	now
"is the host still serving?" probe	one request with a 15 s budget	repeated while a live process holds the endpoint without answering; a reply or a refusal decides
parent's client connect	one attempt, 5 s	same retry rule
reaping the host child	SIGKILL after 60 s, then host_exit == -1	waitpid without a deadline
the host child's cohort join	45 s deadline	UINT64_MAX: waits for locks, answers a conflicting holder at once

The retry rule uses what the daemon API already reports. A failed status or connect still carries muted_endpoint_holder_pid, which is nonzero only when a live process accepted the connection and didn't answer in time. Each attempt keeps the API's finite 5 s budget, so a mute endpoint is not spun in a hot loop. A wedged child is left to the harness's per-suite ceiling.

cli_scope_fixture_finish keeps the environment after an early setup failure. Every cli_scope test calls finish, even when start failed. A start that failed before saving HOME, CBM_CACHE_DIR and SHELL had finish "restore" them to nothing, which unset them for every later test in the suite. finish now restores only what start saved.

Not changed: the 2 s probe that checks an already-drained host has stopped serving (CLI_SCOPE_HOST_DRAINED_PROBE_MS). It's recorded as a separate question. The daemon_* cohort fixture near the top of the file also keeps its own 45 s join.

Tests

• cli_scope_fixture_finish_keeps_env_after_an_early_failure: fails on main at ASSERT(home_kept) and passes with this change.
• cli_scope_retries_a_mute_endpoint_until_it_answers: checks the retry rule on scripted outcomes (mute, mute, mute, answered → true after 4 attempts; mute, refused → false after 2; answered → true after 1).
• All cli_scope tests pass against a real host child.

Checks

• Affected suites (daemon_version daemon_application cli, macOS ASan): 444 passed, 0 failed. make lint-ci clean.
• Local 3-OS ladder on this exact tree:
  • macOS (scripts/test.sh): 9,137 passed, 0 failed, 11 skipped (177 suites); cli 358/0
  • Linux arm64 container (run.sh test): 8,975 passed, 0 failed, 10 skipped (173 suites); cli 359/0
  • Windows arm64 VM (win.sh test, the runner's full 177-suite list): 8,961 passed, 0 failed, 91 skipped. The cli_scope fixture is POSIX-only (it forks), so its tests are not built on Windows. Windows guards (CI's TEST_SEAMS=1 build): 8/8 green.