feat: add apimatic sdk skill

[Ayeshas09]

Adds a new skill for generating, customizing, and managing SDKs using the APIMatic CLI.

What's included:

• SKILL.md having full workflow covering auth, generation, CodeGen settings via APIMATIC-META.json, and change tracking for customizations
• Reference files for all CodeGen setting categories (timeout, branding, endpoints, serialization, etc.)
• First-time setup guide and save-changes workflow
• Example flows
• Eval suite

[sohaibtariq]

PR Review: apimatic-sdk skill

The skill is well-architected overall — strong eval suite (41 cases), clean progressive disclosure, and the 14-item red flags section is the best part of the SKILL.md. Two blocking issues need resolution before merge.

Blocking:

• B1. Missing scripts/auth-login.mjs — runtime failure on first use (see inline comment)
• B2. --track-changes contradicts between SKILL.md and the example file (see inline comments)

Suggestion:

• I3. Add a publishing example file to examples/ (see inline comment)

Details inline below.

Additionally, in terms of the structure of SKILLs.md, it might make sense to have 3 sections:

• Generate an SDK
• Customize an SDK
• Publish an SDK

The last 2 are covered, but the first isn't explicitly mentioned, although it is implied in both of the sections.
Do you think we need to have a separate SDK generation section ?

[Ayeshas09]

PR Review: apimatic-sdk skill

The skill is well-architected overall — strong eval suite (41 cases), clean progressive disclosure, and the 14-item red flags section is the best part of the SKILL.md. Two blocking issues need resolution before merge.

Blocking:

• B1. Missing scripts/auth-login.mjs — runtime failure on first use (see inline comment)
• B2. --track-changes contradicts between SKILL.md and the example file (see inline comments)

Suggestion:

• I3. Add a publishing example file to examples/ (see inline comment)

Details inline below.

Additionally, in terms of the structure of SKILLs.md, it might make sense to have 3 sections:

• Generate an SDK
• Customize an SDK
• Publish an SDK

The last 2 are covered, but the first isn't explicitly mentioned, although it is implied in both of the sections. Do you think we need to have a separate SDK generation section ?

Reagrding the last point, the generation steps were already there, I've grouped them under a Generate an SDK heading and added a note that these same steps apply when initializing change tracking during a customization workflow. So now all the three sections are explicitly covered.