fix(utils): report runtime config probe errors

[chennaji9]

What does this PR do?

loadRuntimeConfigFromDir probes for config.json and the config.d drop-in directory but ignores the error codes of those probes:

std::error_code ec;
if (std::filesystem::exists(configPath, ec)) { ... }
...
if (std::filesystem::is_directory(configDPath, ec)) { ... }

When the query itself fails — e.g. config.json is a symlink loop (ELOOP) or a parent lost search permission (EACCES) — the probe returns false and the failure is silently treated as "no configuration": the caller gets success with an empty optional instead of an error.

Probe with status() and distinguish real failures from absence:

• file_type::none (status could not be determined) is reported as a LINGLONG_ERR with the path and ec.message();
• not_found keeps meaning legitimately absent (POSIX reports an error_code for ENOENT as well, so checking ec directly is not a valid absence test — this is why the fix keys off the status type instead).

Validation

Three new unit tests (using the public loadRuntimeConfig(configDirs, appId, instance) overload):

• LoadRuntimeConfigWithSymlinkLoop — config.json as a self-referential symlink returns an error;
• LoadRuntimeConfigWithConfigDSymlinkLoop — config.d as a self-referential symlink returns an error;
• LoadRuntimeConfigWithoutConfig — empty config dir still returns success with an empty optional (regression guard).

ELOOP is privilege-independent, so the tests behave the same for any user. Full result: ctest -R RuntimeConfig → 29/29 Passed (26 pre-existing + 3 new); ll-tests builds cleanly.

🤖 Generated with Claude Code

[deepin-ci-robot]

Hi @chennaji9. Thanks for your PR.

I'm waiting for a OpenAtom-Linyaps member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
libs/utils/src/linglong/utils/runtime_config.cpp	75.00%	0 Missing and 2 partials ⚠️

Files with missing lines	Coverage Δ
libs/utils/src/linglong/utils/runtime_config.cpp	43.41% <75.00%> (+3.57%)	⬆️

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