feat(cli): add API v2 AgentInstance workflows

[codyhartsook]

Summary

• Adds API v2 CLI commands for AgentTemplate discovery and AgentInstance lifecycle and invocation
• Adds typed AgentInstance and upstream A2A clients over the shared gRPC connection
• Connects through configured gRPC or a temporary controller port-forward, with optional TLS
• Removes the legacy client-side agent project workflow while retaining mcp

Note that of the 64 files changed, 35 were removals from the legacy CLI project workflow ; no server-side APIs or controllers are removed.

This is the first of three related CLI PRs:

1. #2559 : API v2 CLI foundation: template/instance discovery, create/delete, invoke/streaming, JSON output, and quarantining legacy commands.
2. #2605 : TUI: browse AgentInstances, load history, and chat through the same A2A path as invoke.
3. #2606 : Cleanup: simplify main.go and align the command structure with agentregistry.

Suspend and resume are deliberately not exposed by this CLI work.

Related to #2366 and the K13 CLI cutover in docs/plans/api-v2-execution-plan.md.

Test plan

• make -C go test
• go test ./core/cli/...
• make -C go lint
• make -C go build
• AgentTemplate and AgentInstance CLI smoke test against a local installation

[EItanya]

Initial review, I'm still looking for more simplifications, but this is a good start

[EItanya]

This API is still technically supported. Is there a way we can retain this functionality?

[codyhartsook]

tracing this again, the wizard was only used by the removed add-mcp command and wrote to the legacy kagent.yaml project workflow. From my understanding, I think it should remain deleted, with AgentTemplate manifests as the mcp binding but open to suggestions

[EItanya]

The following just merged: 76cde41

We can get this out of clientside code

[codyhartsook]

Yep, done. I removed the client-side create/delete validation and left that to the shared Protovalidate interceptor. The CLI just generates a request ID when one is not supplied.

[EItanya]

Can we please delete this file and viper, it's just complicated.

[codyhartsook]

I removed the internal config package and Viper/ishell from the CLI. Root flags now pass through a small explicit connection options struct. Viper still shows up indirectly through the lint tooling, but the CLI no longer uses it.

[codyhartsook]

note that the code line count decreased but added some file change churn, fyi to reviewers