#2558 tests: the MCP server's tests do not see a Strata server this PC already runs on 8080

本文

Same family as #1935 (tests that pass or fail depending on the PC), not in its list.

**What it changes.** `tools/strata_mcp.py`'s tools look at the default port (8080) and at every config's port. The
fake Strata folder in `tools/test_strata_mcp.py` wrote its configs with port 8080 (the fake `setup.py` and
`write_config()`), and the default port was the real one. On a PC that runs Strata on 8080 (the normal install), the
`StartStop` tests found that server in the fake folder's status: `test_start_status_bench_stop`,
`test_loading_then_ready`, `test_status_sees_other_programs_on_the_port` failed and
`test_never_kills_an_unrelated_process` errored (`'loading' not found in 'Strata is running on port 8080:
swift-1.5-iq3_s, idle; installed: q2_0'`), and `test_plan_then_install` sent `/health`, `/status`, `/metrics` and
`/v1/status` to the real server. Each test now gets a free port of its own in `FakeRoot.setUp`: `M.DEFAULT_PORT` is
patched to it, the fake `setup.py` writes it into the configs it makes, and `write_config()` uses it unless a test
names a port. `test_plan_then_install` also checks that nothing is reported running.

**What it leaves alone.** `tools/strata_mcp.py`, and what every test checks. Tests that already chose a port with
`free_port()` keep it.

**How it was checked.** On this PC (Ubuntu, Python 3.14) with Strata 0.1.44.1 serving on 127.0.0.1:8080:
`python3 tools/test_strata_mcp.py` gives 3 failures and 1 error on `upstream/main`, and 24 OK with this change in 13
of 14 runs (one run had 1 error I could not reproduce in 13 more runs; I did not find which test). With a wrapper
that counts socket connections to port 8080, the suite makes none (it made one with only the default-port part of
this change). Not run on a PC with nothing on 8080.

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