feat(tabs): tab-to-tab agent communication via short handles

Add send_to_tab / read_tab tools so an agent can message or read another
tab by a git-style short handle (shortest unique prefix of the tab UUID,
min 4 chars), shown in the tab bar.

- core/db/tabs: resolveTabPrefix + shortestUniquePrefix (open tabs only,
  LIKE-sanitized prefix matching)
- new tools read-tab.ts / send-to-tab.ts (+ tests) decoupled from the DB
  TabRow via a minimal ResolvedTabRef projection
- agent-manager: unified deliverMessage routing (busy -> queue, idle ->
  new turn) shared by POST /chat and send_to_tab; agent->agent auto-wake
  budget (MAX_AGENT_AUTO_WAKES) to bound ping-pong loops
- summon/loader: send_to_tab + read_tab as grantable tools
- frontend: shortHandleFor + handle badge in TabBar; perm toggles
- notes: tab-comm / user-agents / todo-redesign plans
- chore: biome format fixes (debug-logger, summon.test)

Refs notes/plan-tab-comm.md

1 files changed, 2 insertions, 2 deletions

diff --git a/packages/core/src/agents/loader.ts b/packages/core/src/agents/loader.ts
index 333716e..f4a6c5a 100644
--- a/packages/core/src/agents/loader.ts
+++ b/packages/core/src/agents/loader.ts
@@ -108,8 +108,8 @@ export function expandAgentToolNames(tools: string[]): string[] {
 			default:
 				// Pass through tool names that aren't permission-group
 				// aliases (summon, retrieve, web_search, youtube_transcribe,
-				// todo, and the granular file tools themselves if a user
-				// hand-wrote them in a TOML).
+				// send_to_tab, read_tab, todo, and the granular file tools
+				// themselves if a user hand-wrote them in a TOML).
 				expanded.add(t);
 		}
 	}