docs: clarify docker context use affects all terminal sessions

[vibhuanand]

Fixes #3064

- What I did
Clarified the behavior of docker context use in the CLI documentation.
The docs now explicitly mention that this command updates the Docker CLI configuration and therefore changes the default context globally (affecting all terminal sessions).

Added examples showing how to temporarily select a context using:

• the DOCKER_CONTEXT environment variable
• the --context flag for individual commands

- How I did it

Updated the documentation file:

docs/reference/commandline/context_use.md

Added explanation that docker context use modifies the CLI config and is therefore "sticky". Also added examples demonstrating safer alternatives for temporary context selection.

- How to verify it

1. Open the updated documentation page:
   docs/reference/commandline/context_use.md

2. Confirm the description explains that:

   • docker context use modifies the CLI config
   • the change affects all terminal sessions

3. Confirm examples exist for:

   • docker --context <context>
   • export DOCKER_CONTEXT=<context>

- Human readable description for the release notes

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[vvoland]

Oh, failure related:

ERROR: no start marker in context_use.md

[vvoland]

Oh, failure related:

ERROR: no start marker in context_use.md