docs(wiki): capture session-inbox-monitor received-msg FP as concept

New page concepts/session-inbox-monitor-received-msg-fp.md — sibling of
delegate-task-negative-trigger-fp. Same FP family, new dimension: the carve-out
is already literal+routed (NOT for handling a received message ->
inter-session-peer-discipline) but the route target is not installed, so it has
no competitor and the nearest in-domain skill wins anyway. Borderline (neg 2/3,
EN twin clean), self-corrects on body-load. Bidirectional cross-link +
index + log. New principle: a routed negative competes only if its route
target is installed. Captured in the wiki (not private memory) per owner direction.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.wiki/index.md

@@ -48,6 +48,7 @@ Catalog of all wiki pages. One line per page, organized by type. Updated on ever
 - [using-tasks-status-archival.md](concepts/using-tasks-status-archival.md) — `using-tasks` v1.3.0 done-task archival rule (≥10 🟢 → `.tasks/archive/YYYY-MM.md`) fixes STATUS.md bloat; documents why `tasks_get_status` (single-task, by slug) / `tasks_aggregate` (cross-project cache) can't replace the orientation board-read, so the literal task instruction was not followed
 - [delegate-task-negative-trigger-fp.md](concepts/delegate-task-negative-trigger-fp.md) — `delegate-task` v0.2.1 FP fix: «создать задачу себе» stem-matched the «создать задачу на агента» positive trigger; abstract "does NOT apply when doing the work yourself" carve-out loses to literal stem-match under the 1%-rule → made the negative literal + routed (→ using-tasks). Verified pos 5/5, neg 4/5 (was 0/5)
 - [using-markitdown-cli-migration.md](concepts/using-markitdown-cli-migration.md) — `using-markitdown` v1.0.0→v1.0.1 (PATCH): rewrote from the Docker-based `mcp__markitdown__convert_to_markdown` MCP tool to the native `markitdown` CLI (0.1.6, on PATH); dropped the host→container `file://` mount caveat; container decommission is by image ancestor (`--filter ancestor=markitdown-mcp:latest`), not by the non-existent name `markitdown-mcp`
+- [session-inbox-monitor-received-msg-fp.md](concepts/session-inbox-monitor-received-msg-fp.md) — sibling of [[delegate-task-negative-trigger-fp]]: `session-inbox-monitor` FP-fires on RU «обработай полученное письмо» (N1) because its literal+routed carve-out points at `inter-session-peer-discipline`, which **isn't installed** → no competitor, nearest inbox-skill wins. Borderline (neg 2/3, EN twin clean), body-load self-corrects. **Open** (follow-up task). New principle: *a routed negative competes only if its route target is installed*
 - [task-format-design.md](concepts/task-format-design.md) — new `task-format` skill v0.1.0: public reference for the on-disk `.tasks/STATUS.md` block format the poller parses (header regex, status emoji, `**Weight:**` / `**Notify:**` / `**Requirements:**`); ships with `factory` where the internal wiki/MCP-source can't reach; distinct from [[delegate-task]] (MCP-tool delegation) and [[using-tasks]] (board mechanics); RED 3-baseline / GREEN 2-verify per writing-skills; ground truth = `status-md.ts` + `claim.ts` + `fleet-router.js`
 
 ## Packages