Fixes #329: [Fleet Execution] Implement StitchCli Agent CLI Example

[davideast]

Fixes #329

Implements the requested Agent CLI example showcasing how an LLM can use the Stitch SDK programmatically via structured JSON input/output, schema introspection, and agent best practices.

Labels: fleet-merge-ready
Milestone: 1

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PR created automatically by Jules for task 17785460359496064639 started by @davideast

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⚠️ Closed by fleet-merge: batch conflict resolution dispatched (session 5860293050553752988).

[google-labs-jules]

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[jules-fleet]

🔄 Batch conflict resolution in progress

This PR is part of a batch being resolved together: #309, #332, #333, #334, #335, #336, #337, #338, #339, #341, #342, #340, #343
A Jules session has been dispatched to create a combined PR that resolves all conflicts.

Session: 5860293050553752988