fix: make bundled skill frontmatter discoverable

[nahiyankhan]

Overview

Category: fix
User Impact: Agents can discover the installed Ghost skill instead of silently skipping its malformed metadata.

Problem: The bundled skill and schema-reference descriptions contain unquoted : in YAML frontmatter. On current main, installation and ghost skill check succeed because the bytes match the bundle, but the real Goose skill loader omits ghost because its metadata does not parse.

Solution: Encode both descriptions as folded YAML scalars, preserving their text and the newer main guidance. Add installed-bundle parsing tests and an opt-in test against the real host discovery loader. This complements #294's file-integrity check; it does not change that command's contract.

File changes

packages/ghost/src/skill-bundle/SKILL.md
Make the description valid YAML without changing its value or the skill instructions.

packages/ghost/src/skill-bundle/references/schema.md
Fix the same metadata encoding issue in the bundled schema reference.

packages/ghost/test/skill-bundle.test.ts
Reproduce the malformed header and validate the installed skill's metadata and bundled reference frontmatter.

packages/ghost/test/goosed-skill-discovery.test.ts
With GOOSE_BIN set, verify that the real loader rejects malformed metadata and discovers the installed fixed skill in an isolated workspace/profile. Ordinary test runs skip this host-dependent test.

.changeset/fix-ghost-skill-frontmatter.md
Record a patch release for the discovery fix.

Verification

Validated against main 7cc2e21d:

• Reproduced invalid YAML and real-host omission on unmodified main; ghost skill check still passed as intended.
• pnpm build and pnpm check pass.
• Full suite with the real-host test enabled: 332 passed.
• Commit hooks: 331 passed, 1 opt-in test skipped; checks and formatting pass.
• Real discovery tested with Goose 1.49.0 via GOOSE_BIN=/path/to/goosed.

A separate natural-agent workflow smoke was blocked by authentication before any model work. This PR verifies parsing and discovery, not autonomous workflow invocation. No Berd implementation, evaluation data, or session logs are included.