[FEATURE] Add .shellcheckrc for ShellCheck configuration

[WilliamBerryiii]

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Problem Statement

ShellCheck currently runs via MegaLinter without a dedicated configuration file. This means:

• Shell dialect defaults must be auto-detected per file
• Optional checks like require-variable-braces are not enabled
• SC1091 requires 10 individual inline # shellcheck disable= directives across 13 files
• Direct tool usage outside MegaLinter requires manual flag configuration

Proposed Solution

Create .shellcheckrc configuration file at repository root with project-specific settings:

# ShellCheck configuration for edge-ai repository
shell=bash
source-path=SCRIPTDIR
external-sources=true
enable=require-variable-braces
enable=require-double-brackets
enable=deprecate-which
disable=SC1091

Integrate with MegaLinter by adding to .mega-linter.yml:

BASH_SHELLCHECK_CONFIG_FILE: .shellcheckrc

Alternative Solutions

• Continue using inline directives (increases maintenance burden)
• Use only MegaLinter defaults (misses optional checks aligned with bash.instructions.md)

Target Components

• Terraform modules
• Bicep modules
• Blueprints
• GitHub Actions
• Documentation
• Other: MegaLinter configuration, shell scripts

Implementation Ideas

1. Create .shellcheckrc at repository root
2. Add BASH_SHELLCHECK_CONFIG_FILE: .shellcheckrc to .mega-linter.yml
3. Review and remove redundant inline # shellcheck disable=SC1091 directives (10 occurrences)
4. Validate with shellcheck -x scripts/*.sh

Additional Context

Metric	Value
Shell Scripts in Repo	96 files
Shell Dialect	96% Bash
Existing Inline Directives	19 across 13 files

Benefits

• Enables optional checks aligned with .github/instructions/bash.instructions.md
• Eliminates 10 redundant inline disable directives
• Enables direct ShellCheck usage outside MegaLinter
• Centralizes shell script linting configuration

Potential Challenges

• May surface new warnings from enabled optional checks (require-variable-braces, require-double-brackets)
• Some scripts may need updates to comply with stricter rules