fix(tools/looker): refactor looker-git-branch tool into 5 separate tools

[drstrangelooker]

Description

refactor looker-git-branch tool into 5 separate tools with proper annotations to isolate readonly and destructive tool actions

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[drstrangelooker]

got this feedback on another tool -

This new tool doesn't align well with our Style Guide https://mcp-toolbox.dev/reference/style-guide/. Not blocking, but take a look

Mixing Read and Write Operations
The most significant violation is the combination of list, get, create, update, and delete operations into a single tool > via an operation parameter.

Style Guide Rule: "Never mix read and write logic in a single function. This enables clear consent models where users can auto-approve low-risk reads but must manually approve destructive writes" (source).

This change addresses the same problem with this tool.

[gemini-code-assist]

Code Review

This pull request refactors Looker git branch management by splitting the monolithic project_git_branch tool into five specialized tools: list_git_branches, get_git_branch, create_git_branch, switch_git_branch, and delete_git_branch. The changes include new Go implementations, updated documentation, and revised integration tests. Feedback was provided to correct the copyright year in several new files, which is currently set to 2026.