OpenClaw skill frontmatter fails Codex YAML parsing

Codex CLI 0.145.0 reports three skill-load failures on startup:

```text
failed to load skill .../gstack-openclaw-ceo-review/SKILL.md: invalid YAML: mapping values are not allowed in this context at line 2 column 168
failed to load skill .../gstack-openclaw-investigate/SKILL.md: invalid YAML: mapping values are not allowed in this context at line 2 column 77
failed to load skill .../gstack-openclaw-office-hours/SKILL.md: invalid YAML: mapping values are not allowed in this context at line 2 column 73
```

Introduced by merge commit `b3cd3fd68b03b386ef30e2bba2a6884ccd96a1f3` / release PR #832. The plain-scalar `description:` values contain unquoted `: ` sequences such as `Four modes:` and `Two modes:`, which YAML parses as a mapping delimiter. Repro: install that gstack revision, then run `codex review --base ` (or start Codex with those skills discoverable). Quote or block-format the affected descriptions, and add a test using Codex-compatible YAML parsing for every shipped `SKILL.md` frontmatter.

Inspect the frontmatter in gstack-openclaw-ceo-review/SKILL.md, gstack-openclaw-investigate/SKILL.md, and gstack-openclaw-office-hours/SKILL.md, focusing on their description values. Reproduce the failure with Codex-compatible YAML parsing, then quote or block-format the affected descriptions and add a test covering every shipped SKILL.md frontmatter.

Written by the indexing model from the issue text.