feat(#756): add official Discord channel adapter

docs/reports/code-review/756-code-review.md

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+# Independent Code Review — #756 Official Discord Channel Plugin
+
+**Verdict: APPROVE**
+
+## Scope reviewed
+
+Complete current uncommitted #756 delta: multi-binding trusted agent selection, privileged ingress-route validation, attachment validation/persistence/resume, egress route lifecycle and idempotency, concurrent gateway stream state, Discord lifecycle/thread/rate behavior, compatibility ingress, and tests.
+
+## Review result
+
+No blocking or change-request finding remains.
+
+- **Trusted multi-agent routing:** each binding requires a provisioned `agentConfigId`; the gateway resolves that config server-side, verifies its logical-agent name, and never accepts a Discord-controlled agent selection or applies generic routing to Discord ingress.
+- **Auth and route integrity:** allowlist, pairing, role, and canonical logical-agent/channel-or-thread conversation-route validation occur before gateway processing. Privileged approval/stop paths use the same binding and route validation.
+- **Attachments:** ingress rejects malformed, over-bounded, credential-bearing, fragment-bearing, or query-bearing URLs. Valid attachment metadata, including `sizeBytes`, persists and is reconstructed into resume history as explicitly untrusted context.
+- **Discord reliability:** the adapter supports degraded Socket.IO reconnect, parent/thread routing semantics, bounded pre-side-effect ingress rates, and terminal response-route cleanup. Egress validates route/message alignment, sends deterministic nonces, distinguishes permanent from transient errors, and uses bounded retries.
+- **Concurrent state:** per-client/conversation keys isolate listener, redaction, tool, and stream state for simultaneous threads sharing a Discord socket; disconnect cleanup covers all associated conversations.
+- **Harness neutrality:** contracts retain logical-agent/channel data only; no harness/provider identity leaks into adapter routes or message boundaries.
+
+## Verification performed
+
+- `git diff --check` — passed.
+- `pnpm --filter @mosaicstack/discord-plugin typecheck` — passed.
+- `pnpm --filter @mosaicstack/discord-plugin lint` — passed.
+- `pnpm --filter @mosaicstack/discord-plugin test` — passed: 44 tests; coverage 92.18% statements/lines, 86.55% branches, 100% functions (all ≥85% threshold).
+- `pnpm --filter @mosaicstack/gateway typecheck` — passed.
+- `cd apps/gateway && pnpm exec vitest run src/plugin/discord-ingress.security.spec.ts src/chat/chat.gateway-redaction.spec.ts src/__tests__/integration/tess-cross-surface.integration.test.ts` — passed: 32 tests.

docs/reports/documentation/756-discord-plugin-checklist.md

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+# Documentation Completion Checklist — #756 Official Discord plugin
+
+## Required artifacts
+
+- [x] `docs/PRD.md` includes the #756 workstream, assumptions, and acceptance criteria.
+- [x] User workflow updated in `docs/tess/USER-GUIDE.md`.
+- [x] Administrator configuration and authorization policy updated in `docs/guides/admin-guide.md`.
+- [x] Developer/plugin authoring guidance updated in `docs/tess/PLUGIN-GUIDE.md`.
+- [x] Channel architecture updated in `docs/architecture/channel-protocol.md`.
+- [x] Package operations/development guide added at `plugins/discord/README.md`.
+- [x] `docs/SITEMAP.md` links the official channel plugin documentation.
+
+## API coverage
+
+- [x] No HTTP or WebSocket endpoint was added, removed, or changed.
+- [x] No OpenAPI update is needed.
+- [x] Shared TypeScript contracts are documented in architecture and plugin-authoring guides.
+- [x] Discord authentication, authorization, thread failure, and control-command behavior are documented.
+
+## Structural standards
+
+- [x] Working notes remain under `docs/scratchpads/`.
+- [x] Review and checklist artifacts remain under `docs/reports/`.
+- [x] No generated publishing output was added.
+- [x] Existing repository documentation structure was preserved; no unrelated root cleanup was attempted.
+
+## Review gate
+
+- [x] Independent documentation/contract review passes (shared-contract review plus final code review of the current documentation delta).
+- [x] Independent code review verifies documentation matches implementation (`docs/reports/code-review/756-code-review.md`: APPROVE).
+- [x] Independent security review verifies documented controls (`docs/reports/security/756-security-review.md`: APPROVE).
+
+## Publishing
+
+- [x] Canonical source remains in-repository.
+- [x] No external publishing action is in scope for this slice.

docs/reports/security/756-security-review.md

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+# Security Review — Issue #756
+
+**Scope:** final current uncommitted Discord plugin, shared channel contract, gateway ingress, AgentService, and plugin registration delta  
+**Snapshot:** `plugins/discord/src/index.ts` SHA-256 `5ee6b6aa4e2ff349f137f76b918d02c1254e12066cb48b136048e57bef36fdb2`  
+**Verdict:** **APPROVE**
+
+## Final remediation verification
+
+| Area | Current evidence | Result |
+|---|---|---|
+| Attachment confidentiality and integrity | Ingress accepts bounded attachment metadata only when URL is HTTPS, query-free, fragment-free, and credential-free. Count, aggregate size, field length, MIME, and finite non-negative size validation apply before dispatch; `sizeBytes` is signed and retained. | Pass |
+| Trusted agent selection | Each binding names a required trusted `agentConfigId`; gateway resolves that config server-side and requires its configured name to equal the binding logical-agent ID. Client/provider input cannot select the agent for Discord ingress. | Pass |
+| Privileged operation routing | Gateway revalidates the binding and requires the signed conversation identity to match the configured logical agent before approve/stop actions. Paired admin identity and one-time approval checks remain enforced. | Pass |
+| Egress containment and delivery | Egress requires an aligned message/route, configured parent or exact observed thread target, and cleans response routes after completion, errors, typed-ingress failure, or bounded-map pressure. | Pass |
+| Side-effect limits | Per guild/authorized-parent/user rolling message and thread limits execute before thread creation or dispatch. | Pass |
+
+## Security controls reviewed
+
+- Default-deny guild, parent-channel, user, configured pairing, and role checks precede rate consumption and all side effects.
+- Gateway independently enforces Discord service authentication, HMAC integrity, allowlists, binding/role checks, attachment validation, and replay-ID rejection.
+- Thread authorization uses only the Discord thread parent; category parents cannot authorize ingress.
+- Agent-visible attachment references are explicitly labeled untrusted; binary content is not embedded. Persisted attachment name/URL values are redacted.
+- Egress uses deterministic nonces, bounded transient retry, typed terminal errors, and does not send to forged targets.
+- No secrets or message content were added to plugin logs.
+
+## Verification evidence
+
+| Command | Result |
+|---|---|
+| `pnpm --filter @mosaicstack/discord-plugin test` | PASS — 44 tests; v8 coverage: 92.18% statements/lines, 86.55% branches, 100% functions |
+| `pnpm --filter @mosaicstack/discord-plugin typecheck` | PASS |
+| `pnpm --filter @mosaicstack/types typecheck` | PASS |
+| `pnpm --filter @mosaicstack/gateway typecheck` | PASS |
+| `pnpm --filter @mosaicstack/gateway exec vitest run src/plugin/discord-ingress.security.spec.ts src/agent/__tests__/agent-service-ownership.test.ts` | PASS — 29 tests |
+| `git diff --check` | PASS |
+
+No unresolved critical, high, medium, or low security findings were identified in the reviewed final delta.