Add a new step at the beginning for checking existing skills

[npinto]

Problem

The current skill extraction workflow jumps straight into creating new skills without checking if related skills already exist. This leads to:

• Duplicate skills covering the same problem
• Fragmented knowledge across multiple skills
• Missed opportunities to improve existing skills

Solution

Add Step 1: Check for Existing Skills to the extraction process, creating a "discover before create" workflow.

Changes

README.md

• Fix duplicated sentence typo

SKILL.md

• Add new Step 1 with search commands for finding related skills
• Renumber existing steps (1→2, 2→3, etc.)
• Include decision matrix for update vs create scenarios
• Add versioning guidance (patch/minor/major)

New Step 1 includes

• Goal statement: Find related skills before creating
• Search commands: List skills, keyword search, exact error match, context markers
• Decision matrix with 6 scenarios:
  • Nothing related → Create new
  • Same trigger and fix → Update existing
  • Same trigger, different root cause → Create new with cross-links
  • Partial overlap → Add "Variant" subsection
  • Same domain, different problem → Create new with See also
  • Stale or wrong → Mark deprecated
• Versioning guidance: patch/minor/major definitions
• Tie-breaker: Open closest match and compare before deciding