Adds the remaining 5 plugin capabilities + 7 worker→host RPC methods (interactions read/respond, approvals read/respond, attachment read) needed by the Slack chat gateway plugin (v0.5.0) to pass manifest capability validation and load.
- Security review: PASS (LOOA-642) after the viewer-role privilege-escalation blocker (LOOA-648) was fixed on this branch (requireActiveHumanMember now rejects viewer on impersonation write-paths, matching assertCompanyAccess).
- CI: Build, Typecheck, all server suites (3/3 + serialized 4/4), workspaces, e2e shard 2/2, and all security scanners (Snyk/Socket/Superagent/Greptile/security-review) green.
- One e2e flake (signoff-policy 'non-participant cannot advance stage') is unrelated: it exercises execution-policy stage advancement (routes/issues.ts, untouched by this PR) and failed on a heartbeat_run_events FK race + 409 checkout conflict.
Unblocks LOOA-629 (Slack gateway go-live) and the interview-ask feature.
Co-Authored-By: Paperclip <noreply@paperclip.ing>
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