Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@tests/functional/test-problem-detection.sh`:
- Line 5: The cd command in tests/functional/test-problem-detection.sh should
fail fast like the other scripts: update the cd "$(dirname "$0")/../.."
invocation to check its exit status and abort on failure (e.g., append an
immediate failure handler such as || exit 1 or an equivalent error message +
exit) so the script stops if the directory change fails.

In `@tests/functional/test-topology-discovery.sh`:
- Line 5: The script currently runs cd "$(dirname "$0")/../.." without checking
for failure; update the script so the cd command's failure is detected and
handled (for example, test the exit status of cd or enable errexit) and exit
with a clear error message; specifically modify the invocation around cd
"$(dirname "$0")/../.." (or the script's top-of-file bootstrapping) to abort the
script and log why (unable to change to the expected working directory) when the
cd fails.

In `@tests/functional/test-topology-operations.sh`:
- Line 5: The cd command cd "$(dirname "$0")/../.." should fail fast if it
cannot change directories; update that line to check the exit status and abort
on failure (e.g., append a conditional OR that prints an error to stderr and
exits non‑zero), or ensure the script enables strict failure (set -e) before
running the cd; target the exact cd invocation (cd "$(dirname "$0")/../..") when
applying the change.

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@tests/functional/test-named-channels.sh`:
- Around line 129-131: The DROP DATABASE cleanup currently suppresses stderr and
ignores failures for the command `$COMPOSE exec -T mysql2 mysql -uroot
-ptestpass -e "DROP DATABASE IF EXISTS extra_db;"`; change this so failures are
detected and cause the test run to fail: remove the `2>/dev/null` suppression,
capture and check the command exit status (or enable `set -e`/`set -o errexit`
for the script), and on non-zero exit print a clear error message and exit
non-zero so stale state cannot leak into later tests.

In `@tests/functional/test-problem-detection.sh`:
- Line 23: The mysql state-changing exec lines (e.g. the call using $COMPOSE
exec -T mysql2 mysql -uroot -ptestpass -e "$STOP_SQL") suppress stderr and
ignore exit codes; update each such mutation call (including analogous
START/INSERT/UPDATE/DELETE commands) to capture stdout/stderr and check the
command's exit status immediately, and if non-zero print a descriptive error
including the captured stderr and exit non-zero to fail the test fast. Locate
the commands by the pattern "$COMPOSE exec -T mysql* mysql -uroot -ptestpass -e
\"...\"" and modify them to redirect/collect stderr (or assign output to a
variable), test $? (or the command result), and abort with an explanatory
message when the command fails.
- Around line 100-105: The current check marks CLEARED when only SQL_RUNNING is
"True", which can pass while IO_RUNNING is "False"; update the conditional that
sets CLEARED (the block using SQL_RUNNING, IO_RUNNING, CLEARED and REPL_STATE)
to require both SQL_RUNNING = "True" and IO_RUNNING = "True" before setting
CLEARED and breaking the loop, and adjust the echo message to reflect both
thread states (e.g., "SQL=True, IO=True") so the test only passes when both
threads are healthy.
- Line 15: discover_topology is being treated as optional but must be a hard
precondition; update the test to fail immediately when discover_topology
"mysql1" returns non-zero by checking its exit status and exiting with a
non-zero code and an explanatory stderr message (e.g., run discover_topology
"mysql1" and if it fails print "Topology discovery failed for mysql1" to stderr
and exit 1), or alternatively enable strict shell error handling at the top of
the script (set -euo pipefail) to enforce failure; refer to the
discover_topology invocation to locate where to add the check.
- Around line 5-6: The script should fail fast if bootstrap steps fail: add a
strict shell flag (e.g., set -euo pipefail or at minimum set -e) at the top of
the script (immediately after the shebang) so that failures in the cd "$(dirname
"$0")/../.." or source tests/functional/lib.sh commands abort the run; ensure
the flags are applied before those two lines so any failure in cd or source
stops the script.

---

Nitpick comments:
In `@tests/functional/test-named-channels.sh`:
- Line 65: The loop variable `i` in the `for i in $(seq 1 15); do` line is
intentionally unused and should be renamed to `_` to avoid the SC2034
unused-variable warning; update the loop to `for _ in $(seq 1 15); do` and
verify there are no references to `$i` elsewhere (if any exist, replace or
remove them) so the change is safe.