fix: Correct CSV header output handling

[fukusuket]

Closed #282
It was caused by an extra comma being appended at the end of the CSV header.
I expect this issue to be resolved with this fix. Could you please confirm?🙏

Integration-Test

• https://github.com/Yamato-Security/takajo/actions/runs/20320716712

[Copilot]

Pull request overview

This PR fixes a trailing comma bug in CSV header generation for two timeline commands. The old code used a loop that appended a comma after each header field, resulting in an extra comma at the end of the header line. The fix replaces this with the join(",") method which correctly doesn't add a trailing comma.

• Refactored CSV header writing to use join(",") instead of loop-based concatenation
• Applied the fix consistently to both timelineTasks and timelineLogon commands
• Aligns with the pattern already used in several other files in the codebase

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/takajopkg/timelineTasks.nim	Replaced loop-based header concatenation with join(",") to eliminate trailing comma in CSV header output
src/takajopkg/timelineLogon.nim	Replaced loop-based header concatenation with join(",") to eliminate trailing comma in CSV header output

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[YamatoSecurity]

@fukusuket That fixed it. Thanks so much!!!