Split agent-skills-spec into separate authoring and client integration guides

Reorganize the spec documentation:
- agent-skills-spec.md now serves as an index linking to the guides
- skill-authoring.md covers skill creation and SKILL.md format
- skill-client-integration.md provides guidance for Skill Client implementors

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

spec/agent-skills-spec.md

@@ -1,55 +1,13 @@
 # Agent Skills Spec
 
-A skill is a folder of instructions, scripts, and resources that agents can discover and load dynamically to perform better at specific tasks. In order for the folder to be recognized as a skill, it must contain a `SKILL.md` file. 
+A skill is a folder of instructions, scripts, and resources that agents can discover and load dynamically to perform better at specific tasks. In order for the folder to be recognized as a skill, it must contain a `SKILL.md` file.
 
-# Skill Folder Layout
+## Guides
 
-A minimal skill folder looks like this: 
-
-```
-my-skill/
-  - SKILL.md
-```
-
-More complex skills can add additional directories and files as needed.
-
-
-# The SKILL.md file
-
-The skill's "entrypoint" is the `SKILL.md` file. It is the only file required to exist. The file must start with a YAML frontmatter followed by regular Markdown. 
-
-## YAML Frontmatter
-
-The YAML frontmatter has 2 required properties:
-
-- `name`
-    - The name of the skill in hyphen-case
-    - Restricted to lowercase Unicode alphanumeric + hyphen
-    - Must match the name of the directory containing the SKILL.md
-- `description` 
-    - Description of what the skill does and when Claude should use it
-
-There are 3 optional properties:
-
-- `license`
-    - The license applied to the skill
-    - We recommend keeping it short (either the name of a license or the name of a bundled license file)
-- `allowed-tools` 
-    - A list of tools that are pre-approved to run
-    - Currently only supported in Claude Code
-- `metadata`
-    - A map from string keys to string values
-    - Clients can use this to store additional properties not defined by the Agent Skills Spec
-    - We recommend making your key names reasonably unique to avoid accidental conflicts
-
-## Markdown Body
-
-The Markdown body has no restrictions on it.
-
-# Additional Information
-
-For a minimal example, see the `template-skill` example.
+- [Skill Authoring Guide](skill_authoring.md) — How to create skills, including folder layout and SKILL.md format
+- [Skill Client Integration Guide](skill_client_integration.md) — How to add Skills support to a new agent or product
 
 # Version History
 
+- 1.1 (2025-12-16) Added guidance for Skill Client implementors.
 - 1.0 (2025-10-16) Public Launch