Makes the TaskYou Claude Code channel multi-GM aware, consuming the new assigned_gm field shipped in bborn/taskyou#561 (the ty binary now sets TASK_ASSIGNED_GM on event hooks and accepts --assigned-gm on ty create).

What

When several GMs share a single TaskYou daemon, the channel now:

1. Stamps the tasks it creates with --assigned-gm <GM_SLUG> — only on ty create, idempotent (skipped when the caller already passed --assigned-gm).
2. Filters the events it surfaces to the current GM — emits an event when its assigned_gm matches this GM's slug, or when it's unassigned and the GM opts into seeing unassigned events (SEE_UNASSIGNED, default true).

Files (additive — no deletions):

• templates/channel/taskyou-channel.ts.tmpl — new GM_SLUG (process.env.GM_SLUG || process.env.GM_ALIAS || {{GM_ALIAS}}) and SEE_UNASSIGNED consts; --assigned-gm auto-injection on ty create (idempotent); notification filter in pollNotifications (the line cursor always advances — only the emit is gated, so nothing is lost from the read position); assigned_gm added to the emitted notification meta.
• templates/hooks/task.completed.tmpl, templates/hooks/task.blocked.tmpl — emit "assigned_gm": "$TASK_ASSIGNED_GM" in the JSON line.
• config.example.env — documents GM_SLUG (derives from GM_ALIAS) and SEE_UNASSIGNED.

Why

Channel-side companion to #561: it turns the daemon's per-task GM attribution into actual per-session event routing, so one shared daemon fans tasks/notifications out to the correct GM instead of broadcasting every event to every GM.

Additive on top of #28 (the channels integration) and independent of the local-mode/macOS work (#31) — branched directly off #28 so it's cleanly mergeable on its own (verified zero-conflict merge with #31 in either order). Fully backward-compatible: with no config and an older ty (no assigned_gm), SEE_UNASSIGNED defaults to true, so unassigned events still surface and tasks are stamped with the GM's existing alias. The SSH/remote command path is untouched.

How tested

• Channel template: rendered with sample setup env (GM_ALIAS=acme); GM_SLUG substitutes to the alias default. bun build clean (transpile + full bundle against the MCP SDK).
• Hook templates: bash -n clean; rendered task.completed with TASK_ASSIGNED_GM set and a quote-containing title emits valid, correctly-escaped JSON with assigned_gm populated.
• Confirmed the diff has no file deletions and touches only the four named templates.