fix(cli): surface compose-flags resolver failures instead of silencing them

[w3-surfer]

Fixes #1876.

Problem

_regenerate_compose_flags in ods-cli ran the resolver with stderr discarded, and removed the cache on failure:

"$INSTALL_DIR/scripts/resolve-compose-stack.sh" \
    ... \
    > "$INSTALL_DIR/.compose-flags" 2>/dev/null || rm -f "$INSTALL_DIR/.compose-flags"

resolve-compose-stack.sh already prints an actionable diagnosis when it can't run:

ERROR: PyYAML is required by resolve-compose-stack.sh for compose validation.
       Or install manually: <python> -m pip install pyyaml

but 2>/dev/null threw it away. As reported in the issue, ods enable <ext> then appeared to succeed and the real failure only surfaced two commands later as compose's no configuration file provided: not found, with no hint of the cause.

Fix

Capture the resolver's stderr and print it after a warning that names the consequence, so the failure is reported where it happens:

local resolver_err=""
if ! resolver_err=$("$INSTALL_DIR/scripts/resolve-compose-stack.sh" \
    ... \
    2>&1 > "$INSTALL_DIR/.compose-flags"); then
    rm -f "$INSTALL_DIR/.compose-flags"
    warn "Could not regenerate the compose stack cache. 'ods start' will fail until this is resolved:"
    [[ -n "$resolver_err" ]] && printf '%s\n' "$resolver_err" >&2
fi

The 2>&1 > file ordering keeps stdout going to .compose-flags and captures only stderr, so successful runs behave exactly as before.

Also corrected the lib/service-registry.sh warning, which said only "Service registry will be incomplete" while lifecycle commands actually break. It now states that ods enable / ods start will fail.

Verification

Extracted the real function and ran it against a stub resolver covering both paths:

Resolver fails (stub reproduces the PyYAML error):

WARN: Could not regenerate the compose stack cache. 'ods start' will fail until this is resolved:
ERROR: PyYAML is required by resolve-compose-stack.sh for compose validation.
       Or install manually: python3 -m pip install pyyaml
.compose-flags removed

Resolver succeeds: stderr empty, .compose-flags contains -f docker-compose.base.yml -f docker-compose.nvidia.yml.

bash -n passes on both files.

Out of scope

The issue also suggests a host-Python PyYAML preflight check on the macOS install path. That is a larger, separate change and is not included here.

[w3-surfer]

@nolanmak thanks for the precise diagnosis here, it made this a quick fix. If you were already planning to take it yourself, say the word and I'll close this in favor of yours.