…n-registry — interrupt now actually interrupts (#2342)

`src/auto-reply/reply/get-reply-run.ts` (hot path for every inbound
auto-reply) had hardcoded `const isActive = false; const isStreaming =
false;` at the queue-mode gate. This collapsed every user-configured
queue mode to the "no run active" branch, breaking `interrupt` /
`steer` / `steer-backlog` / `collect` semantics. A user who set
`queue.mode: interrupt` in their config got silently downgraded — the
interrupt mode never actually interrupted a running CLI subprocess.

## Fix

- Wire `isActive` to `isSessionRunActive(queueKey)` from
  `src/agents/session-run-registry.js` (the registry populated by
  `ChannelBridge` at register/unregister sites).
- Wire `interrupt` queue mode to `killSessionRun(queueKey)` — when
  `isActive` is true and mode is `interrupt`, dispatch
  `abortController.abort()` or `SIGTERM` to the running subprocess
  before starting the new run.
- Delete the dead `sessionLaneKey` / `laneSize` / `clearCommandLane`
  block at lines 402-408 — the issue noted (and grep confirmed)
  `command-queue.ts` lanes are `main`/`cron`/`subagent`/`nested`;
  there is no session-keyed lane that this code populates.
- Drop `isStreaming` entirely. CLI runtimes don't expose a "streaming"
  state distinct from "active" — the distinction was Pi-embedded-era.
  Binary: active = streaming. Removed the param from
  `RunPreparedReplyParams` / `runReplyAgent`'s contract and deleted
  the dead `shouldSteer && isStreaming` branch at `agent-runner.ts:193-200`
  (inside that branch `const steered = false` made the inner block
  unreachable anyway).
- Drop unused `shouldSteer` from `runReplyAgent` contract and the
  local declaration in `get-reply-run.ts` (only consumer was the
  deleted dead branch).

## Changes

- `src/auto-reply/reply/get-reply-run.ts`:
  - Import `isSessionRunActive`, `killSessionRun` from
    `../../agents/session-run-registry.js`.
  - Drop unused `clearCommandLane`, `getQueueSize` imports.
  - Replace hardcoded `isActive = false` with registry call.
  - Replace hardcoded interrupt-mode no-op with
    `killSessionRun(queueKey)`.
  - Delete `shouldSteer` local + `isStreaming` pass-through.
- `src/auto-reply/reply/agent-runner.ts`: remove `isStreaming`,
  `shouldSteer` from `runReplyAgent` params; delete the
  `shouldSteer && isStreaming` dead branch (9 lines).
- Test fixtures (`agent-runner.media-paths.test.ts`,
  `agent-runner.misc.runreplyagent.test.ts`,
  `agent-runner.runreplyagent.e2e.test.ts`): remove stale
  `isStreaming: false` and `shouldSteer: false` properties that
  no longer exist on the contract.

## Verification

- `pnpm check` (format + tsgo + lint + project-specific lints) → exit 0
- `pnpm test` (full parallel suite) → **800 files / 7010 passed /
  3 skipped** — no regression
- Rescan: `git grep "isEmbeddedPiRunActive\|isEmbeddedPiRunStreaming\|resolveEmbeddedSessionLane"`
  in `src/` returns zero hits.
- Rescan: `git grep "isStreaming"` in `src/auto-reply/` returns zero
  hits (test fixtures cleaned).

Closes #2342

Refs: #2089, #2088

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>