Remove .ai-team/ deprecation banner (no longer needed after rename) #71

Summary

In v0.4.1, we added a deprecation banner warning users about the .ai-team/ → .squad/ rename coming in v0.5.0 (see #70). Now that v0.5.0 has shipped the rename, the banner is no longer needed and should be removed.

What to remove:

1. CLI (index.js): Remove the deprecation banner from squad init and squad upgrade output
2. Coordinator prompt (squad.agent.md): Remove the deprecation notice section from Team Mode
3. Templates: Remove any deprecation comments from generated files

Acceptance Criteria

• No deprecation banner appears after squad init
• No deprecation banner appears after squad upgrade
• No deprecation notice in squad.agent.md coordinator prompt
• No stale references to issue Rename .ai-team/ to .squad/ with backward-compatible migration #69 in CLI output

Related

• Rename .ai-team/ to .squad/ with backward-compatible migration #69 — Rename .ai-team/ to .squad/ with backward-compatible migration
• Add deprecation banner warning users about .ai-team/ → .squad/ rename in v0.5.0 #70 — Add deprecation banner warning users about the rename