🤖 fix: add explicit char limit to workspace name prompt

[ethanndickson]

Summary

Adds explicit character limit guidance to workspace name generation prompts to prevent AI models from generating names that exceed the 20-character schema limit.

Background

AI models (especially Haiku) don't always respect JSON schema numeric constraints—they need explicit guidance in the prompt text. The schema already had .max(20) but the AI wasn't seeing this constraint, resulting in names like "workspace-integration" (21 chars) that fail validation:

AI_NoObjectGeneratedError: No object generated: response did not match schema.
...
"code": "too_big",
"maximum": 20,
"message": "Too big: expected string to have <=20 characters"

Implementation

Added "max 15 chars" to both:

1. The schema .describe() text
2. The prompt requirements text

The 15-char target leaves room for the -xxxx suffix that gets appended, while the 20-char schema constraint remains as a safety net.

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Generated with mux • Model: anthropic:claude-opus-4-5 • Thinking: high • Cost: $0.45