fix(config): parse structured config values

[HengYangDS]

Summary

• Parse YAML list literals for list-valued configuration defaults.
• Parse YAML mapping literals for mapping-valued defaults, including quick_commands.
• Preserve existing string, scalar, unknown-key, and nested-key coercion behavior.

Verification

• scripts/run_tests.sh tests/hermes_cli/test_set_config_value.py tests/hermes_cli/test_config.py tests/hermes_cli/test_config_validation.py tests/hermes_cli/test_config_drift.py tests/hermes_cli/test_config_env_expansion.py tests/hermes_cli/test_config_env_refs.py -- -q
  • 259 passed, 0 failed.
• ruff check hermes_cli/config.py tests/hermes_cli/test_set_config_value.py
  • passed.

TDD evidence

Before the production change, the new list/mapping regression tests failed because both values were persisted as strings (57 passed, 2 failed). After the minimal change, the same test file passed (59 passed, 0 failed).

[alt-glitch]

This was generated by AI during triage.

Related: this overlaps open structured-value coercion work in #40546, #64389, #59182, and #37460. This PR is narrower (known declared list/mapping defaults only), so it is not marked a duplicate; maintainers can choose the desired validation scope.

[HengYangDS]

Closing as superseded by #64389.

#64389 contains this PR's list/mapping coercion fix and additionally validates known scalar/structured types, rejects malformed or non-JSON-compatible values before any write, and covers config-to-env round trips. Keeping one stronger review surface avoids duplicate maintenance.