Document the two real device bugs found running the compose test on-device

Both fixes (is_network_in_use()'s ip-exit-code misread, and the
kill_session()-vs-async-cleanup race) plus the INFO()-based diagnostics
that made finding them possible are now documented in
test_compose_orchestrator.cpp's own CLAUDE.md entry, alongside
confirmation that the full [integration][root][net] suite (73 assertions,
14 cases) passes cleanly on the real Android target device.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gv3s5jckJKzh6JkMoi2Akz

CLAUDE.md

@@ -590,6 +590,62 @@ Source layout (all under `src/`):
     `--list-networks`/`--list-volumes`/`ps` all confirmed clean afterward
     (only the pre-existing, unrelated `test-preexisting-net`/other real
     volumes remained, untouched).
+
+    **Two real bugs found and fixed running this same test on the actual
+    Android target device, not assumed** (both in `is_network_in_use()`/
+    its caller — `network_bridge.{h,cpp}`/`commands.cpp` — never in this
+    test file itself, which needed no changes beyond gaining better
+    diagnostics — see below):
+    1. `is_network_in_use()` treated any nonzero exit from `ip -o link
+       show master <bridge>` as "the check itself failed" and failed
+       closed (assumed in use). But the device's own minimal `ip` build
+       exits **1**, not 0, for the "bridge exists, nothing attached" case
+       this project's dev machine reports as exit 0 with identical (empty)
+       output — confirmed by direct on-device inspection
+       (`nsenter --net=... -- ip -o link show master <bridge>` returned
+       empty stdout with exit 1 for a bridge that genuinely had nothing
+       attached). Fixed by splitting into two checks: first confirm the
+       bridge device itself is reachable at all (`ip link show <bridge>`,
+       unfiltered — fail closed only if *that* fails or is empty), then
+       decide "in use" purely from whether the *filtered* membership
+       query's own output is non-empty, regardless of its exit code.
+    2. Even with that fixed, the device still failed the same way:
+       `-d/--down` checked `is_network_in_use()` mere milliseconds after
+       `kill_session()` returned, and it was still correct — the tap
+       device genuinely hadn't been detached from the bridge yet.
+       Root cause: `kill_session()` only waits for the *sandboxed
+       process itself* (via its cgroup) to die; the separate,
+       independently scheduled daemonized process that started it
+       (running `run_mounted_container()`, blocked in its own `waitpid()`
+       on bwrap) still has its own post-exit cleanup left to run
+       (`stop_tap_relay()` among it) before a tap+relay join's host-side
+       device is actually removed from the bridge — confirmed in the
+       device's own debug log, where the kill and the "still in use"
+       check landed single-digit milliseconds apart. Fixed with a new
+       `network_becomes_unused()` (`commands.cpp`, `.cpp`-local),
+       retrying `is_network_in_use()` for up to 10s
+       (`nanosleep()`-based, matching this project's existing polling
+       style) instead of giving up on the very first still-attached
+       answer.
+
+    **Diagnostics added while chasing this, kept permanently**: both
+    `-u`/`-d`'s own captured stdout (`CapturedStdout` otherwise silently
+    swallows `compose_up_command()`/`compose_down_command()`'s own
+    `fmt::print()`/`spdlog` output — spdlog's default sink is stdout, same
+    as this project's plain status lines) are now attached via Catch2's
+    `INFO()`, which only actually prints alongside a failing assertion in
+    the same scope — without this, the device failure would have had no
+    diagnostic trail at all. The port-forward reply check's own
+    `REQUIRE(reply.has_value())` was also softened to `CHECK` -- a flaky
+    reply on one run must never skip the `-d/--down` cleanup below it.
+
+    **Verified end to end on the real Android target device itself**
+    (root, over SSH — see `reference_device_ssh_access.md`): after both
+    fixes, the full `-u`/`-d` lifecycle test passes cleanly (18
+    assertions), and the entire `[integration][root][net]` suite (73
+    assertions, 14 test cases, including this one) passes with nothing
+    regressed. `--list-networks`/`--list-containers`/`ps` all confirmed
+    clean afterward.
   - `tests/support/fixtures.{h,cpp}` — `g_test_app_config` (a plain `AppConfig`
     global, default-constructed) is set once by `run_self_tests()`
     (`self_test.cpp`, see above) from the current `-t` run's own effective,