Fast test/plan-route.test.ts: the planner's route proved without a whole crew run, every test under 1 s #1438

Part of #1242. test/plan-route.test.ts joined the gate from main without being listed (#1170). Measured alone: 5.6 s for the file, and "the planner's run is refused with no_pillar, then opens the issues under the umbrella" takes 4.9 s, because it waits for a whole crew run of the stand-in agent. It sits in SLOW in scripts/gate.ts with this issue beside it.

Chop and rewrite, not trim (the owner, on #1242):

• Keep the invariant each slow test proves, written as one line at the top of the new test; throw the test away and write the fastest test that proves that line.
• One forge and one server per file, created in beforeAll; no Bun.sleep, a fake clock; in-memory SQLite unless the disk is the point; fixtures built once per file; no chromium, no bwrap, no real network in the gate.
• Slow by nature moves to NIGHTLY in scripts/gate.ts, with its reason.

Done: the gate's scripts/test-times.json shows every test in the file at or under 1 s, and the file's SLOW entry is removed in the same pull.

Parked by the crew: the check failed ("the gate's list > every test/*.test.ts is in exactly one list, and every entry exists") and the decider saw no point in another try (pull #1442 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.