test: close the DB-suite hermeticity + vacuous-skip gaps

Three related fixes from the test audit.

**The CLI journey fixture gets its own database.** It spawned a real picloud —
whose dispatcher/orchestrator claim loops are global by design (one instance owns
one database) — against the shared dev DB, so it could claim the manager-core
suites' outbox/workflow rows (the same class of bug already fixed for the e2e
suites, one binary over). It now clones one dedicated database per journey run
from the migrated template. test-support gains `named_test_db_url` (explicit
stable name) + a blocking wrapper for the sync `LazyLock` fixture. The one journey
that talks to Postgres directly (dead-letter injection) now uses the fixture's DB
URL, not the base DATABASE_URL, so it hits the database the server reads.

**workflow_orchestrator moves to per-test databases.** Its `claim_ready_step` is
global, so the old harness serialized every test behind a process-wide CLAIM_LOCK
AND ran `DELETE FROM workflow_runs` (unscoped — it wiped every app's runs) before
each one. A private database per test makes the global claim see only that test's
rows, so both the lock and the unscoped DELETE are deleted.

**DB-backed suites fail loud instead of skipping green.** ~15 manager-core suites
`return None` when DATABASE_URL is unset and report PASS — so in any environment
that lost its database the entire integration surface reports green while running
nothing (why the CI gap went unnoticed for so long). New
`picloud_test_support::abort_if_db_required` panics when `PICLOUD_REQUIRE_DB` is
set (CI now sets it) but DATABASE_URL is not, injected into each suite's skip
path. Local runs without the var still skip cleanly.

Mutation-verified: with PICLOUD_REQUIRE_DB=1 and DATABASE_URL unset, a suite
panics; without the var it skips.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Cargo.lock

@@ -1965,6 +1965,7 @@ dependencies = [
  "libc",
  "percent-encoding",
  "picloud-shared",
+ "picloud-test-support",
  "postgres",
  "predicates",
  "reqwest",