Add deprecation banner warning users about .ai-team/ → .squad/ rename in v0.5.0 #70

Summary

Starting in v0.4.1, Squad should display a deprecation banner alerting users that v0.5.0 will rename the .ai-team/ directory to .squad/. The goal is to give early adopters advance notice so they're not surprised, and to link them directly to the tracking issue for the rename.

Banner Behavior

When to show:

• On every squad init or squad upgrade — print the banner after the operation completes
• On every Squad session start (in squad.agent.md) — the coordinator shows the banner as part of its first response greeting, alongside the version number

What to show:

⚠️  Heads up: In v0.5.0, the .ai-team/ directory will be renamed to .squad/.
    A migration tool (squad upgrade --migrate-directory) will handle the transition.
    Details: https://github.com/bradygaster/squad/issues/69

Where to implement:

1. CLI (index.js): After squad init and squad upgrade complete, print the banner to stdout. Use yellow/warning color if available.

2. Coordinator prompt (squad.agent.md): Add a section near the top of Team Mode that instructs the coordinator to include the banner in its first response of each session. Something like:

   **Deprecation notice (v0.4.1–v0.4.x only):**
   When greeting the user or acknowledging the first message, include:
   > ⚠️ Heads up: In v0.5.0, .ai-team/ will be renamed to .squad/.
   > A migration tool will handle the transition. [Details →](https://github.com/bradygaster/squad/issues/69)

3. Templates: The banner should also appear in templates/workflows/ or any generated output that references .ai-team/ paths, as a comment.

Acceptance Criteria

• Banner displays after squad init in the CLI
• Banner displays after squad upgrade in the CLI
• squad.agent.md instructs the coordinator to show the banner on session start
• Banner includes the direct URL to issue Rename .ai-team/ to .squad/ with backward-compatible migration #69
• Banner is clearly visible but not blocking (informational, not an error)
• Banner only appears in v0.4.1–v0.4.x (removed in v0.5.0 — see linked removal issue)

Related

• Rename .ai-team/ to .squad/ with backward-compatible migration #69 — Rename .ai-team/ to .squad/ with backward-compatible migration