Bug: frontmatter sanitizer skips hyphenated keys, so allowed-tools breaks command/agent files

Description

sanitize() in packages/core/src/config/markdown.ts exists so that "other coding agents accept unquoted colons in frontmatter values" keep working (comment on line 20). But its key pattern is:

const entry = line.match(/^([a-zA-Z_][a-zA-Z0-9_]*)\s*:\s*(.*)$/)

The character class has no -, so any hyphenated key fails to match, hits if (!entry) return [line], and is returned unsanitized. The retry matter(sanitize(content)) then throws exactly as the first attempt did.

This is unfortunate because allowed-tools is the single most common such key in other agents' command files - precisely the compatibility case the function was written for (see #6985 for .claude/commands/ compatibility).

Steps to reproduce

.opencode/command/review.md:

---
allowed-tools: Read: every file
description: Review helper
---
Review my code.

Actual - ConfigMarkdown.parse() throws Failed to parse YAML frontmatter: incomplete explicit mapping pair. Via parseOption() the error is swallowed and the whole frontmatter block leaks into the body:

data:    {}
content: "---
allowed-tools: Read: every file
description: Review helper
---
Review my code."

Expected:

data:    { "allowed-tools": "Read: every file", "description": "Review helper" }
content: "Review my code."

An underscore key is the control case and works fine - allowed_tools: Read: every file sanitizes correctly. Dotted keys (tools.read:) fail the same way as hyphenated ones.

Impact

Since parseOption() swallows the error and decode still returns a structurally valid object, the failure is silent:

• Commands (config/plugin/command.ts:71) run with the raw YAML header, --- delimiters and all, pasted into the prompt sent to the model.
• Agents (config/plugin/agent.ts:154) lose description, mode, model, steps and permissions entirely, and system becomes the raw file.
• Skills (skill.ts:84) go through the same path.

OS

Windows (platform-independent - pure regex logic)