fix(stop): add --name flag to stop named contexts and instances

[AdeshDeshmukh]

Problem

The microcks stop command only supports stopping the instance associated with the current context. There is no way to target a specific instance by name — even though microcks start --name <name> and microcks login --name <name> already allow users to create named contexts and instances.

This asymmetry means that after starting multiple instances or logging into multiple servers, users have no direct way to stop a specific one without first switching context.

Root Cause

When a user runs microcks start --name myinstance, the CLI stores the context with:

• Context name = http://localhost:8585 (the server URL)
• Instance field = myinstance (the user-given name)

So a naive lookup by context name alone (ResolveContext(myinstance)) fails — there is no context literally named myinstance. The existing ResolveContext expects the context's name field, not the Instance field.

Solution

This PR adds a --name flag to microcks stop with a two-tier fallback resolution:

1. Try as a context name — works for contexts created via microcks login --name dev (stored as Context{Name: "dev"})
2. Scan contexts by Instance field — works for contexts created via microcks start --name myinstance (stored as ContextRef{Name: "http://...", Instance: "myinstance"})

If neither lookup succeeds, the user receives a clear error message.

When --name is omitted, behavior is 100% identical to the current code (uses the current context).

Changes

cmd/stop.go — 29 insertions, 2 deletions:

• Added var name string for the flag variable
• Added Example help text with usage patterns
• Added two-tier context resolution logic
• Registered the --name flag on stopCmd

Verification

Check	Result
go build ./...	✅ Compiles cleanly
All existing tests	✅ Pass (26/27 pass; TestDeleteContext failure is pre-existing)
Backward compatible	✅ No flag = unchanged behavior

Example Usage

# Stop the instance from the current context (existing behavior)
microcks stop

# Stop by context name (useful after login --name)
microcks stop --name dev-context

# Stop by instance name (useful after start --name)
microcks stop --name myinstance

Fixes #438

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds support for stopping a Microcks instance by explicitly specifying a context or instance name via a new --name flag, including updated CLI help/examples.

Changes:

• Add --name flag to microcks stop with updated usage examples.
• Update stop logic to resolve a target context by context name, or fallback to searching by instance name.

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[Vaishnav88sk]

Ptal at Copilot comments.

If start --name and named login contexts exist, stop should also let users target them directly.

The resolution approach looks reasonable, but before merge I’d like targeted tests for:

• resolving by context name,
• resolving by instance name,
• not-found behavior.

I’d also like the precedence to be explicit and tested when a context name and an instance name collide. Right now context lookup wins, which is fine, but it should be intentional.