fix(skilltoolset): document load_skill param as name, not skill_name

[koriyoshi2041]

Closes #912.

The default SkillToolset system instruction tells the model:

use the load_skill tool with skill_name="<SKILL_NAME>"

but the load_skill tool input (skilltool.LoadSkillArgs) marshals its field as name:

type LoadSkillArgs struct {
    Name string `json:"name" jsonschema:"The name of the skill to load."`
}

So the first load_skill call in a session is rejected for an unknown skill_name field and only succeeds after the model retries with name. Updated the instruction to document name="<SKILL_NAME>" to match the schema. (load_skill_resource keeps its own skill_name parameter — that one is unchanged.)

Added TestDefaultInstructionMatchesLoadSkillSchema, which reflects the JSON tag off LoadSkillArgs.Name and asserts the default instruction documents that exact parameter for load_skill (and no longer skill_name=), so the two cannot drift apart again. go test ./tool/skilltoolset/... passes.

[indurireddy-TF]

Thank you for opening this PR. This correctly resolves the schema mismatch in skilltoolset where the default system instruction incorrectly directed models to use skill_name instead of name for load_skill

I have verified the test cases, and they are working as expected.

@kdroste-google @foxfrikses @baptmont , could you please take a look at these changes and review the PR when you have a moment?

[koriyoshi2041]

Rebased this onto current main so the PR is no longer behind. Rechecked the touched skilltoolset package with go test ./tool/skilltoolset/....