Add social connector host foundation

[oratis]

What changed

• adds the researched Sense social connector architecture and platform rollout plan
• defines and strictly validates social-connector.json manifests
• adds revisioned social drafts with immutable SHA-256 approval snapshots, expiry, and one-shot claim semantics
• surfaces connector manifests and draft state through lisa sense social
• preserves MCP tool annotations as metadata without treating untrusted hints as authorization

Why

Conversation-driven publishing needs a host-enforced trust boundary before any platform connector can publish. Connecting an account must not silently authorize a post, and model-visible tools must not bypass the user final confirmation.

Impact

This is the host foundation only; it does not publish to a live platform. Follow-up stacked PRs add the draft-only host tool/API/UI and the first Bluesky/Mastodon connectors.

Validation

• npm run typecheck
• node --import tsx --test src/mcp/client.test.ts src/sense/social/manifest.test.ts src/sense/social/drafts.test.ts
• git diff --check

[oratis]

Post-merge review finding:

mutate() currently sorts every draft and applies .slice(-MAX_DRAFTS). That can evict a non-terminal draft (approved/publishing) when enough newer drafts exist. A connector may then publish successfully while completeSocialDraftPublish() can no longer find the draft to persist receipts, leaving an externally visible post with no durable host outcome.

I am addressing this in a dedicated follow-up: retain every non-terminal draft, prune only terminal history, and reject new drafts once the active-draft ceiling is reached.