feat(teams): add opt-in Connector reactions

[NeoHsu]

Important

Stacked draft: logical base stack/teams-04-owned-mutations is PR #1495. GitHub requires an upstream PR base to exist in openabdev/openab, so this draft temporarily targets main and may show preceding stack layers. Do not merge it until #1495 is merged and this branch is rebased onto current main; then review only its single incremental commit.

What problem does this solve?

Provide opt-in Teams status reactions without changing existing deployments or falling back to content messages.

Discord Discussion URL: https://discord.com/channels/1491295327620169908/1491365158868619404/1531339032527765655
Microsoft Teams roadmap discussion.

Review Contract

Goal

Provide opt-in Teams status reactions without changing existing deployments or falling back to content messages.

Non-goals

Reaction parity outside the documented Microsoft preview surface, arbitrary emoji selection, and default enablement are excluded.

Accepted Residual Risks

The Connector reaction API is public preview and can change. Operators must opt in; failures degrade status display without changing the content result.

Acceptance Criteria

Capability is false by default and advertised only when enabled; targets remain authenticated and owned; add/remove swaps serialize; unsupported or ambiguous outcomes do not cause content fallback or blind retry.

Follow-ups

Revisit the API when Microsoft publishes a stable contract and expand the visual matrix in a safe tenant.

At a Glance

Authenticated Teams activity / operator target
                    │
                    ▼
            [this PR’s bounded layer]
                    │
                    ▼
          explicit outcome or fail-closed stop

Prior Art & Industry Research

OpenClaw: its Microsoft Teams extension separates access checks, Bot Framework route context, and outbound operations. For this slice the relevant comparison is Teams reactions and status updates.

Hermes Agent: its Teams platform adapter keeps Teams-specific transport and message shaping behind a platform adapter. It does not provide OpenAB’s negotiated Core/Gateway outcome contract, so this PR keeps the useful adapter boundary but adds explicit fail-closed semantics.

Proposed Solution

• Add default-off Microsoft Bot Connector reaction support.
• Negotiate reaction capability and map OpenAB status states to Teams reaction IDs.
• Preserve serialized status swaps and bounded retry logging.

Why this approach?

Default-off negotiation isolates a preview API from existing deployments and lets status failures degrade without affecting content.

Alternatives Considered

Enable preview reactions by default (rejected: backward-incompatible) or emulate them with content (rejected: noisy duplicate messages).

Validation

• cargo check -p openab-core
• cargo check -p openab-gateway --features teams