feat(channels): route messages to prefix-specific sessions - #12595

What this PR does

Adds shared messageRoutes configuration so one Channel connection can run multiple prefix-selected workflows with separate conversation sessions and first-turn instructions. An optional defaultMessageRoute names the route for ordinary messages; without it, unmatched chat messages are ignored. The longest matching prefix wins and is removed before dispatch.

Route identity is retained through queued turns, session recovery, group history, and scheduled loops. DWS native document/todo triggers remain independent of IM prefix routing, and Telegram attachments and QQ message formatting preserve the routed message body.

Why it's needed

A single connection often serves more than one purpose, such as reviewing changes and answering repository questions. Prefix routing lets operators provide focused instructions for each workflow without running multiple connections or mixing their conversation sessions.

Reviewer Test Plan

How to verify

1. Configure /review and /QA with different instructions. Send both prefixes in the same chat: each should create a separate session, strip its prefix, and inject only its own instructions on the first turn.
2. Leave the default route unset and send ordinary text: it should not start a session or run a command. Set the default to /QA: ordinary text should reuse the QA session unchanged.
3. Queue multiple review messages while also sending a QA message. The collected review messages should remain in their original route; clearing one route should not clear the other.
4. Restore persisted sessions and run a route-owned scheduled loop. The route identity and instructions should survive. Group history should not cross routes.
5. Verify captioned Telegram attachments, QQ messages with ordinary-text prefixes, and DWS messages after leading mentions. Existing sender/group access policies must continue to apply.

Evidence (Before & After)

Before: one shared instruction set and conversation route per configured session scope.

After: deterministic adapter tests and a built-output integration smoke verify configuration parsing, distinct route sessions, default routing, unmatched-message filtering, first-turn instructions, collect dispatch, and persisted-session recovery. No external IM or model calls were made.

Validation: full workspace build and typecheck; targeted channel-base, DWS, Telegram, QQ, CLI configuration, and settings-management tests; ESLint on changed TypeScript files.

Tested on

Environment (optional)

Local workspace builds with fake transport and bridge implementations; no production service changes.

Risk & Scope

• Main risk or tradeoff: routing is applied before command and memory-intent handling, so shared commands need a matching prefix when no default route is configured.
• Not validated / out of scope: real provider delivery, live model behavior, and route-specific models. Existing Channel memory keeps its chat/thread scope; routes are not an authorization sandbox.
• Breaking changes / migration notes: existing configurations without routes retain their behavior. messageRoutes is currently incompatible with multiSession. No legacy messagePrefix API is introduced. Adapter-generated media placeholders and native provider events remain outside prefix routing.

Linked Issues

None.