TestSys CLI does not return useful yaml formatting errors

Given a test yaml that looks like:

```yaml
---
apiVersion: testsys.bottlerocket.aws/v1
kind: Test
metadata:
name: hello-bones
namespace: testsys-bottlerocket-aws
spec:
agent:
name: hello-agent
image: "example-test-agent:demo"
keep_running: false
configuration:
mode: Fast
person: Bones the Cat
helloCount: 3
helloDurationMilliseconds: 500
resources: []
dependsOn: []
```

and attempting to run it:

```
❯ cli run file example_test_agent.yaml
Unable to read manifest
```

_*Note that the `keep_running` key should be `keepRunning`*_. The CRD key error isn't bubbled up from the underlying `read_manifest`

https://github.com/bottlerocket-os/bottlerocket-test-system/blob/e4c6d22e76cacde344ef0765ed5630edf15ea58e/cli/src/run_file.rs#L17

Still new to rust, but it would be great if a more descriptive error was returned.

Start with cli/src/run_file.rs at the run_file entry point and reproduce the failure with `cli run file example_test_agent.yaml`. Trace how read_manifest reports the invalid keep_running key and determine where its underlying error is discarded. Done means the CLI surfaces a descriptive YAML or CRD validation error instead of only reporting “Unable to read manifest.”

Written by the indexing model from the issue text.