docs: git retry, survey vars, and runner executor configuration

[cursor]

Summary

Documentation-only update to the semaphore-docs submodule, covering recently shipped features and configuration gaps.

Docs added/updated

• Survey variables (docs/user-guide/task-templates/survey-vars.md): multi-select (select) type, text type, default values, environment-variable target, JSON array encoding for multi-select in all delivery paths, parsing examples for Bash/PowerShell/Python
• Task templates (docs/user-guide/task-templates/README.md): per-template executor image override for Docker/Kubernetes runners
• Git retry (docs/admin-guide/configuration.md, config-file.md, troubleshooting.md, faq/troubleshooting.md): git_attempts / SEMAPHORE_GIT_ATTEMPTS, exponential backoff behavior, troubleshooting for intermittent clone/pull failures
• Runner executor env (docs/admin-guide/configuration.md, env-vars.md): SEMAPHORE_RUNNER_EXECUTOR for setting the full executor JSON block

Codepaths covered

• db_lib/GitRepository.go — clone/pull retry with capped exponential backoff
• util/config.go — GitAttempts / SEMAPHORE_GIT_ATTEMPTS, SEMAPHORE_RUNNER_EXECUTOR
• services/tasks/local_executor.go — survey variable targets and multi-select JSON encoding
• Per-template executor_image for Docker/K8s runners

Key knowledge gaps addressed

• Operators had no reference for tuning git clone/pull resilience (git_attempts)
• Survey variable docs listed only four types and omitted multi-select, env targets, and JSON encoding behavior
• SEMAPHORE_RUNNER_EXECUTOR was implemented but missing from the configuration reference

Verification

• Docusaurus build completed successfully (npm run build in docs/ submodule)

Submodule

• semaphore-docs branch: cursor/engineering-documentation-updates-0879 (commit dde80b2)