fix(internet-identity): add frontend canister split

[aterga]

Summary

• Internet Identity now has a separate frontend canister (uqzsh-gqaaa-aaaaq-qaada-cai) alongside the backend (rdmx6-jaaaa-aaaaa-aaadq-cai)
• Updated canister IDs table, identity provider URLs, pitfall guidance, and code example to reflect the split
• id.ai resolves to the new frontend canister; backend.id.ai resolves to the backend

Test plan

• Verified both canister IDs exist on mainnet (same controller and subnet)
• Confirmed id.ai returns x-ic-canister-id: uqzsh-gqaaa-aaaaq-qaada-cai and backend.id.ai returns x-ic-canister-id: rdmx6-jaaaa-aaaaa-aaadq-cai
• Verified @icp-sdk/auth@5.0.0 and @icp-sdk/core@5.2.0 install and all import paths + API methods from the code example resolve correctly
• skill-validator validate passes with no errors
• CI validation

🤖 Generated with Claude Code

[github-actions]

Skill Validation Report

Validating skill: /home/runner/work/icskills/icskills/skills/internet-identity

Structure

• Pass: SKILL.md found

Frontmatter

• Pass: name: "internet-identity" (valid)
• Pass: description: (323 chars)
• Pass: license: "Apache-2.0"
• Pass: compatibility: (31 chars)
• Pass: metadata: (2 entries)

Markdown

• Pass: no unclosed code fences found

Tokens

File	Tokens
SKILL.md body	1,585
Total	1,585

Content Analysis

Metric	Value
Word count	917
Code block ratio	0.35
Imperative ratio	0.11
Information density	0.23
Instruction specificity	1.00
Sections	8
List items	8
Code blocks	2

Contamination Analysis

Metric	Value
Contamination level	low
Contamination score	0.03
Primary language category	config
Scope breadth	2

• Warning: Language mismatch: javascript (1 category differ from primary)

Result: passed

Project Checks

✓ Project checks passed for 1 skills (0 warnings)