fix: support slash-based branch names and multi-dot file extensions in GitHub URL parsing

[useye]

Description

Fixes #1940

This PR fixes two bugs in the CLI:

1. GitHub URL Parsing Bug

Problem: The regex pattern assumed branch names don't contain /, causing failures for valid URLs like:

https://github.com/org/repo/blob/feature/new-validation/spec.yaml

Solution: Rewrote the URL parsing logic to:

• Parse owner, repo, and the combined branch+path
• Work backwards from the filename to separate branch from file path
• Correctly handle branch names with slashes

2. File Extension Detection Bug

Problem: Used name.split('.')[1] which fails for:

• Files with multiple dots: my.asyncapi.yaml → incorrectly gets "asyncapi" instead of "yaml"
• Files without extensions: asyncapi → undefined, causes crash

Solution:

• Use .pop() to get the last segment after splitting by .
• Add proper undefined check for files without extensions
• Convert to lowercase for case-insensitive comparison

---

Testing:

• GitHub URL with slash-based branch (e.g. feature/new-validation) works correctly
• Multi-dot filenames (e.g. my.asyncapi.yaml) are validated correctly
• Files without extensions don't cause crashes

[changeset-bot]

⚠️ No Changeset found

Latest commit: 1ac5021

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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