Fix environment variable mapping for read-only mode

[pinotelio]

Fix environment variable mapping for read-only mode configuration

Add SetEnvKeyReplacer to viper configuration to properly map environment variables with underscores to flag names with dashes. This enables the documented GITHUB_READ_ONLY=1 environment variable to work correctly.

Without this fix, viper was looking for GITHUB_READ-ONLY (with dash) but the documentation and standard convention use GITHUB_READ_ONLY (with underscore).

Fixes issue where read-only mode was not being activated when using GITHUB_READ_ONLY=1 in Docker containers.

Incorrect Read-Only Tools when GITHUB_READ_ONLY=1 passed:

Test with GITHUB_READ-ONLY=1 (Dash):

Correct Result After The Patch:

Requirement	Command	Status
✅ Tests pass	go test -v ./...	PASSED
✅ Linter passes	golangci-lint run	PASSED
✅ Project linter	script/lint	PASSED
✅ Update snapshots	UPDATE_TOOLSNAPS=true go test ./...	COMPLETED
✅ Update docs	script/generate-docs	COMPLETED

Closes:

[pinotelio]

ping @tonytrg :)