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, 26 insertions, 2 deletions

diff --git a/packages/core/tests/agents/loader.test.ts b/packages/core/tests/agents/loader.test.ts
index 88173ea..35ab0cf 100644
--- a/packages/core/tests/agents/loader.test.ts
+++ b/packages/core/tests/agents/loader.test.ts
@@ -22,10 +22,34 @@ describe("expandAgentToolNames", () => {
 		expect(out).toContain("run_shell");
 	});
 
+	it("passes through the tab tools as independent names (no tab_comm group)", () => {
+		const out = expandAgentToolNames(["send_to_tab", "read_tab"]);
+		expect(out).toContain("send_to_tab");
+		expect(out).toContain("read_tab");
+		// Granting only one must not pull in the other.
+		const onlySend = expandAgentToolNames(["send_to_tab"]);
+		expect(onlySend).toContain("send_to_tab");
+		expect(onlySend).not.toContain("read_tab");
+	});
+
 	it("passes through non-group tool names unchanged", () => {
-		const out = expandAgentToolNames(["summon", "retrieve", "web_search", "youtube_transcribe"]);
+		const out = expandAgentToolNames([
+			"summon",
+			"retrieve",
+			"web_search",
+			"youtube_transcribe",
+			"send_to_tab",
+			"read_tab",
+		]);
 		expect(out).toEqual(
-			expect.arrayContaining(["summon", "retrieve", "web_search", "youtube_transcribe"]),
+			expect.arrayContaining([
+				"summon",
+				"retrieve",
+				"web_search",
+				"youtube_transcribe",
+				"send_to_tab",
+				"read_tab",
+			]),
 		);
 	});