docs(teams): update msteams-enterprise.md for Unified Mode (v0.9.0+)

[masami-agent]

Summary

The enterprise Teams deployment guide (docs/msteams-enterprise.md) still documents the standalone gateway mode exclusively. Since v0.9.0, the OAB binary embeds the Teams adapter directly (Unified Mode), which simplifies enterprise deployments significantly.

The self-hosted guide (docs/msteams-selfhosted.md) already has a Unified Mode callout at the top — the enterprise guide should be updated similarly.

What needs updating

1. Add Unified Mode section (recommended path for v0.9.0+)

The enterprise guide should document the simpler deployment where:

• No separate gateway container is needed
• The OAB pod itself serves /webhook/teams on port 8080
• Ingress routes directly to the OAB pod (no gateway in between)
• Configuration uses [teams] section in config.toml (or configToml in Helm values)

2. Document [teams] trust section

The identity-trust-none ADR means Teams users are rejected by default. The enterprise guide should document:

• allow_all_users = true for org-wide access
• allowed_users = ["29:..."\] for restricted access
• How to find a user's 29:... ID from OAB logs

3. Document Helm configToml format

Chart v0.9.0+ requires configToml instead of the old --set agents.kiro.discord.* fields. The enterprise guide still uses the old format:

helm install openab ... --set agents.kiro.gateway.enabled=true

Should show the new configToml approach.

4. Mark standalone gateway as legacy

Similar to how the self-hosted guide has a "Standalone Gateway Mode (Legacy)" heading.

Proposed architecture (Unified Mode, enterprise)

Teams Client → Bot Framework → K8s Ingress (HTTPS) → OAB Pod (:8080/webhook/teams)
                                                       ↑
                                          Single pod, no gateway needed

Context

Tested on v0.9.0-beta.10 with:

• Single Tenant Azure Bot
• [teams] section with allow_all_users = true
• Helm configToml format
• Full round-trip verified (Teams → OAB → kiro-cli → reply → Teams)

References

• Self-hosted guide (already updated): docs/msteams-selfhosted.md
• Trust ADR: identity-trust-none
• Config-first ADR: per-platform configuration (docs(adr): first-class per-platform configuration #1263)