[AIR-3028] qs: fix buildDevBranchName: the functionality is duplicated

[host6]

AIR-3028 qs: fix buildDevBranchName: the functionality is duplicated
https://untill.atlassian.net/browse/AIR-3028

[augmentcode]

🤖 Augment PR Summary

Summary: This PR refactors the qs dev branch-creation flow to remove duplicated functionality and make branch-existence validation consistent.

Changes:

• Simplified gitcmds.CreateDevBranch by removing the internal “remote branch exists” check and its extra parameter.
• Refactored the GitHub-issue workflow: branch name generation is moved into BuildDevBranchName (now returns both branch name and notes derived from the issue title).
• Renamed CreateGithubLinkToIssue to LinkBranchToGithubIssue and reordered the flow so the git branch is created/pushed before attempting GitHub issue linkage.
• Centralized local+remote branch existence checks into internal/commands/dev.go for all workflows (GitHub/Jira/custom).
• Replaced the go-git based branch existence check with direct git CLI calls.
• Added uspecs documentation (change request + implementation plan) describing the rationale and expected pipeline.

Technical Notes: GitHub issue titles are fetched via gh issue view --json title, and dev-branch naming now consistently appends the -dev suffix after sanitization.

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