feat: Phase F-5+F-7 — command-sync + sub-discussion + channel-create tools

Bundles the remaining "agent does things in Fabric" surface, skipping
presence-sync (Plexum's state machine isn't 1:1 with HF status semantics)
and attachments (Plexum has no media pipeline yet) — both deferred.

internal/subdisc/ (~140 LOC + 5 tests): persistent KV at
<profile>/state/plugin-kv/fabric-sub-discussions.json
- Entry: SubChannelID, HostAgentID, HostUserID, GuestUserIDs,
  HostGuide, GuestGuide, CallbackGuildNodeID, CallbackChannelID, CreatedAt
- Open / Lookup / LookupForHost (host-enforcement) / Add / Remove / All
- atomic tmp+rename persistence; corrupt file = start empty

internal/tools/tools.go — 7 new tools:
- create-chat-channel       (xType=general)
- create-work-channel       (xType=work)
- create-report-channel     (xType=report)
- create-discussion-channel (xType=discuss)
- discussion-complete       (post summary + close channel)
- create-sub-discussion     (create + invite + KV store + greeting)
- close-sub-discussion      (host-only; posts callback to parent + closes)

internal/fabric/client.go: CreateChannel / CloseChannel /
JoinChannel / LeaveChannel / SetChannelPurpose / Canvas CRUD /
SyncCommands (added in earlier F-4 commit; reused here)

cmd/plexum-fabric-channel-plugin/main.go:
- subdisc.Store opened from DefaultPath at init; passed into tools.Deps
- HostConfig adds commands_sync_key + sync_commands (defaults
  ["new","stop"]) — F-5 command-sync to every (agent,guild) pair at
  init when key is set; silently skips when omitted
- syncCommandsToGuilds: best-effort PUT per guild, logs per-guild
  outcome

scripts/install.sh: manifest tools[] expanded to 16 entries
(9 from F-4 + 7 new). create-channel variants share a schema shape.

Live verified:
  $ plexum plugin-call create-chat-channel \
      '{"agent_id":"fabrictester","guild_node_id":"test-guild2",
        "name":"plexum-f7-smoke","is_public":true}'
    → "created general channel plexum-f7-smoke (id=6315e636-...)"
  $ plexum plugin-call fabric-channel-list ...
    → 3 channels listed including the new one

F-6 (attachments) + F-5b (presence-sync) + F-8 (coalesce) deliberately
deferred — see DEV-NOTES.

Tests: 5 new in internal/subdisc (27 total in this repo).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/install.sh

@@ -89,7 +89,21 @@ print(json.dumps(out))
       {"name":"fabric-channel","description":"Fetch metadata + member list for a specific channel.",
         "inputSchema":{"type":"object","properties":{"agent_id":{"type":"string"},"guild_node_id":{"type":"string"},"channel_id":{"type":"string"}},"required":["agent_id","guild_node_id","channel_id"]}},
       {"name":"fabric-canvas","description":"Read or write the channel canvas (op: get|share|update|remove).",
-        "inputSchema":{"type":"object","properties":{"agent_id":{"type":"string"},"guild_node_id":{"type":"string"},"channel_id":{"type":"string"},"op":{"type":"string","enum":["get","share","update","remove"]},"title":{"type":"string"},"format":{"type":"string","enum":["md","html","text"]},"source":{"type":"string"}},"required":["agent_id","guild_node_id","channel_id","op"]}}
+        "inputSchema":{"type":"object","properties":{"agent_id":{"type":"string"},"guild_node_id":{"type":"string"},"channel_id":{"type":"string"},"op":{"type":"string","enum":["get","share","update","remove"]},"title":{"type":"string"},"format":{"type":"string","enum":["md","html","text"]},"source":{"type":"string"}},"required":["agent_id","guild_node_id","channel_id","op"]}},
+      {"name":"create-chat-channel","description":"Create a chat channel (xType=general).",
+        "inputSchema":{"type":"object","properties":{"agent_id":{"type":"string"},"guild_node_id":{"type":"string"},"name":{"type":"string"},"is_public":{"type":"boolean"},"member_user_ids":{"type":"array","items":{"type":"string"}},"listeners":{"type":"array","items":{"type":"string"}},"on_duty":{"type":"string"},"purpose":{"type":"string"}},"required":["agent_id","guild_node_id","name"]}},
+      {"name":"create-work-channel","description":"Create a work channel (xType=work).",
+        "inputSchema":{"type":"object","properties":{"agent_id":{"type":"string"},"guild_node_id":{"type":"string"},"name":{"type":"string"},"is_public":{"type":"boolean"},"member_user_ids":{"type":"array","items":{"type":"string"}},"listeners":{"type":"array","items":{"type":"string"}},"on_duty":{"type":"string"},"purpose":{"type":"string"}},"required":["agent_id","guild_node_id","name"]}},
+      {"name":"create-report-channel","description":"Create a report channel (xType=report).",
+        "inputSchema":{"type":"object","properties":{"agent_id":{"type":"string"},"guild_node_id":{"type":"string"},"name":{"type":"string"},"is_public":{"type":"boolean"},"member_user_ids":{"type":"array","items":{"type":"string"}},"listeners":{"type":"array","items":{"type":"string"}},"on_duty":{"type":"string"},"purpose":{"type":"string"}},"required":["agent_id","guild_node_id","name"]}},
+      {"name":"create-discussion-channel","description":"Create a discussion channel (xType=discuss).",
+        "inputSchema":{"type":"object","properties":{"agent_id":{"type":"string"},"guild_node_id":{"type":"string"},"name":{"type":"string"},"is_public":{"type":"boolean"},"member_user_ids":{"type":"array","items":{"type":"string"}},"listeners":{"type":"array","items":{"type":"string"}},"on_duty":{"type":"string"},"purpose":{"type":"string"}},"required":["agent_id","guild_node_id","name"]}},
+      {"name":"discussion-complete","description":"Post a summary then close the channel.",
+        "inputSchema":{"type":"object","properties":{"agent_id":{"type":"string"},"guild_node_id":{"type":"string"},"channel_id":{"type":"string"},"summary":{"type":"string"}},"required":["agent_id","guild_node_id","channel_id","summary"]}},
+      {"name":"create-sub-discussion","description":"Spawn a sub-discussion channel with the caller as host + invited guests.",
+        "inputSchema":{"type":"object","properties":{"agent_id":{"type":"string"},"guild_node_id":{"type":"string"},"name":{"type":"string"},"guest_user_ids":{"type":"array","items":{"type":"string"}},"host_guide":{"type":"string"},"guest_guide":{"type":"string"},"parent_channel_id":{"type":"string"},"greeting":{"type":"string"},"x_type":{"type":"string","enum":["discuss","work","report","general"]}},"required":["agent_id","guild_node_id","name","parent_channel_id"]}},
+      {"name":"close-sub-discussion","description":"Close a sub-discussion the caller hosts and post a callback to its parent channel.",
+        "inputSchema":{"type":"object","properties":{"agent_id":{"type":"string"},"sub_channel_id":{"type":"string"},"summary":{"type":"string"}},"required":["agent_id","sub_channel_id"]}}
     ]'
 
     cat > "${MANIFEST_PATH}" <<EOF