Parallel catalog-filter test run hangs (pre-existing, cross-module)

## What

`cargo test -p codewhale-tui --lib --locked catalog` (default parallel threads)
hangs deterministically on this machine: the test binary sits at ~1.5s CPU
after 6-10 minutes, and libtest's stall warnings name `runtime_api::tests::*`
victims (`output_cap_catalog_reports_exact_transport_support`,
`provider_catalog_and_switch_preserve_each_listed_route_identity`,
`provider_catalog_keeps_official_deepseek_facts_but_not_custom_proxy_claims`,
`provider_catalog_preserves_named_custom_identity_for_new_threads`).

## Evidence it is pre-existing

- Reproduced 3x with #6289 slice-2 changes in the tree (two full-filter
runs, one shard excluding all touched modules).
- Reproduced 1x on a stashed baseline tree (binary relinked after the
stash, same hang signature). Slice 2's production changes are pure
functions; nothing in them can block.
- Single-threaded (`--test-threads=1`) the same filter completes: 246
passed + 1 seed-fallback failure that slice 2 then fixed.
- `runtime_api::tests::` alone in parallel: 228 passed in 15s. The stall is
a cross-module interaction under the `catalog` filter, not one bad test.

## Suspects (unproven)

- Local-only interference: live Codewhale processes (pet serve, app-server)
were listening during these runs, and the runs did not use
`scripts/with-hermetic-test-home.sh` the way CI does.
- A fixed-port `spawn_test_server` collision under this particular filter's
parallelism (e.g. the `127.0.0.1:18190` lm-studio fixture).
- A genuine lock-ordering deadlock between global catalog locks held across
awaits in different modules' tests.

## Acceptance

- [ ] Reproduce (or fail to) under `with-hermetic-test-home.sh` with no live Codewhale processes
- [ ] Identify the wedged test pair via shard bisection or `lldb` backtraces of the stuck binary
- [ ] Fix the ordering/port/global-state interaction so the parallel filter completes

Start by running `cargo test -p codewhale-tui --lib --locked catalog` and repeat it with `scripts/with-hermetic-test-home.sh`, ensuring no live Codewhale processes are running. Use shard bisection or `lldb` backtraces on the stuck binary to identify the wedged test pair, then inspect the fixed-port fixture and global catalog-lock interactions. Done means the parallel catalog filter completes reliably under the hermetic setup.

Written by the indexing model from the issue text.