improve(asset-canister): add WASM version downgrade pitfall

[marc0olo]

Summary

• Adds pitfall #9: downgrading asset canister WASM version can cause "Cannot parse header" panics
• Recommends preferring the @dfinity/asset-canister recipe over type: pre-built with manual WASM URLs
• Notes reinstall mode as an option for intentional downgrades

Addresses #135 (Obs 1), #136 (F4).

[github-actions]

Skill Validation Report

Validating skill: /home/runner/work/icskills/icskills/skills/asset-canister

Structure

• Pass: SKILL.md found

Frontmatter

• Pass: name: "asset-canister" (valid)
• Pass: description: (322 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	3,194
Total	3,194

Content Analysis

Metric	Value
Word count	1,947
Code block ratio	0.39
Imperative ratio	0.11
Information density	0.25
Instruction specificity	0.87
Sections	16
List items	19
Code blocks	9

Contamination Analysis

Metric	Value
Contamination level	low
Contamination score	0.12
Primary language category	shell
Scope breadth	3

• Warning: Language mismatch: config, javascript (2 categories differ from primary)

Result: passed

Project Checks

✓ Project checks passed for 1 skills (0 warnings)