feat: harden support, localize knowledge and add operator availability [skip ci]

Source-only publication of reviewed commit 64e96a7f423673dc29ad56485be9fc79bce8af1c.

Passed in isolation: focused frontend/backend tests, race checks, TypeScript typecheck, lint, Go compilation, Flowgram build, and deterministic SDK build/tests.

Not accepted as a production release: Next.js export/native assembly remains blocked by environment memory limits; browser interaction and MySQL staging acceptance remain unverified. No production server, database/schema, runtime configuration, deployment, release tag, or workflow execution was performed.

Expected source tree: 0a4a7528e9.

docs/hardening/README.md

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+# Security and reliability hardening
+
+This independent fork starts from the current source tree of
+[MonoVerseNS/agent-desk-ng](https://github.com/MonoVerseNS/agent-desk-ng), revision
+`b06954b0a495389cbb5194e0d388342eabe60636`. It does not import the old Git history.
+The upstream Apache-2.0 license and notices remain applicable. This document
+records changes made by this fork; it is not a claim of production certification.
+
+## Integration baseline
+
+The isolated integration reconciles public Gitea main `299ea50f` with the reviewed
+hardening branch `63e04578`. It preserves main's bounded connection attempts,
+abortable ongoing HTTP recovery and System setup navigation alongside the
+identity/live-access/draft/setup safeguards. Only the clean public repository
+history is used. See `VALIDATION.md` for executed checks and unresolved gates.
+
+## Release gate
+
+The hardening changes must be reviewed and validated before deployment. Source
+inspection, a compiler check, a passing isolated test, and live acceptance are
+separate kinds of evidence. See `VALIDATION.md` for the actual checks performed.
+No production service, database, credentials, or external deployment is changed
+by committing this source code.
+
+## Changes being integrated
+
+- Separate guest, signed-user, issuer and channel identities. Use canonical
+  customer/channel WebSocket topics and recheck recipients instead of treating
+  a topic subscription as authorization.
+- Apply conversation-view permission to staff WebSockets; keep notifications
+  separate. Revalidate session expiry, revocation, account state and permissions
+  on long-lived connections. Disabled roles must no longer grant permissions.
+- Keep drafts and asynchronous responses bound to their identity and dialogue.
+  Preserve drafts on failed sends, protect newly typed revisions, and prevent
+  duplicate concurrent sends. Profile refresh and delayed API errors must not
+  restore or expire the wrong signed-in account.
+- Turn setup repair into an explicit preview/apply operation. Never resurrect
+  deleted configuration or silently introduce continuous working hours. Apply
+  reviewed writes transactionally and dispatch only after commit.
+- Make empty setup, initial retry and standalone chat dismissal truthful and
+  recoverable; remove bearer-token-bearing WebSocket URLs from browser logs.
+
+## Upgrade precautions
+
+Customer identity scoping is an additive schema and token-contract change, not
+only a frontend patch. Existing unscoped customer tokens will be rejected.
+Legacy identities and conversations must be inventoried and reconciled with
+trusted issuer/channel provenance before expecting their old history in new
+customer sessions. No automatic customer merge or destructive cleanup is
+appropriate. See `CUSTOMER_IDENTITY_UPGRADE.md` before any deployment.
+
+New anonymous sessions are server-issued. Knowing an old anonymous external ID
+is not sufficient to reclaim its history. Preserve the signed customer-session
+credential for normal resume; loss or expiry can require a new anonymous session.
+
+The setup quick-fix API now requires preview and explicit apply. Older callers
+must not treat a successful preview response as proof that configuration changed.
+See [the setup contract](SETUP_PREVIEW.md) before integrating custom callers.
+
+## Verification priorities
+
+1. Guest/user/channel collisions, unauthorized staff topics, revoked/expired
+   sockets, disabled roles and concurrent identity registration.
+2. Wrong-recipient drafts, failed and duplicate sends, delayed responses after
+   switching conversations or accounts, and logout during profile refresh.
+3. Preview/apply tampering, permission denial, rollback, deleted configuration,
+   off-hours schedules, empty-channel simulation and dispatch failure reporting.
+4. Desktop and narrow-screen interaction checks in Russian, English and Chinese.
+
+Use temporary, isolated data for checks. Do not run migration/repair commands
+against a live database merely to validate the code.