#8095: fix(sessions): include accountId in deliveryContext for outbound per-peer DM sessions

## Summary - When `ensureOutboundSessionEntry()` created a per-peer DM session (e.g. via an agent's messaging tool), it called `recordSessionMetaFromInbound()` which only populated the session's `origin` metadata — it did **not** set `deliveryContext`, `lastChannel`, `lastTo`, `lastAccountId`, or `lastThreadId` - This caused per-peer DM sessions to be missing `accountId` in their delivery context, so subsequent deliveries routed through the default account instead of the bound one (wrong bot) - Fix: replace `recordSessionMetaFromInbound()` with `updateLastRoute()` which properly sets the full delivery context (including `accountId`) and also handles origin metadata when `ctx` is provided **Repro:** agent with a Telegram binding (`accountId: "page"`) + `session.dmScope: "per-peer"` → cron/tool sends to a peer → per-peer session created without `accountId` → reply delivered through wrong bot. ## Test plan - [x] `pnpm build` passes - [x] `pnpm check` (lint + format) passes - [x] `pnpm vitest run src/infra/outbound/` — all 82 tests pass - [x] `pnpm vitest run src/gateway/server-methods/` — all 32 tests pass - [x] `pnpm vitest run src/config/sessions.test.ts` — all 26 tests pass 🤖 Generated with [Claude Code](https://claude.com/claude-code) <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR fixes missing `accountId` (and related route metadata) when creating per-peer outbound DM sessions by switching `ensureOutboundSessionEntry()` to call `updateLastRoute()` instead of `recordSessionMetaFromInbound()`. `updateLastRoute()` writes a normalized `deliveryContext` (`channel`, `to`, `accountId`, `threadId`) and also derives origin metadata from `ctx`, preventing replies from routing through the default account/bot. The gateway send mirroring test was updated accordingly to mock/expect `updateLastRoute()`. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk. - The change is narrowly scoped (swap to `updateLastRoute` and pass the needed fields) and aligns with existing session-store behavior; the updated test reflects the new dependency and the described test plan indicates targeted Vitest suites were run. - No files require special attention <!-- greptile_other_comments_section --> **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->